MASTER 

NEGA 


NO 


02-80747-3 


MICROFILMED  1992 
COLUMBIA  UNIVERSITY  LIBRARIES/NEW  YORK 


as  pari  of  the  .      „    •    ,„ 

"Foundations  of  Western  Civilization  Preservation  Project 


Funded  by  the  xttt^tcc 

NATIONAL  ENDOWMENT  FOR  THE  HUMANITIES 

Reproductions  may  not  be  made  without  permission  from 

Columbia  University  Libiaiy 


COPYRIGHT  STATEMENT 


The  copyright  law  of  the  United  States  ~  Title  17,  United 
States  Code  ~  concerns  the  making  of  photocopies  or  other 
reproductions  of  copyrighted  materiaL.. 

Columbia  Universitv  Library  reserves  the  right  to  refuse  to 

accept  a  copy  order  if,  in  its  judgement,  fulfillment  of  the  order 
would  involve  violation  of  the  copvrisht  law. 


AUTHOR 


OSBORN,  HENRY 
FAIRFIELD 


TITLE: 


THE  ORIGIN  AND 
EVOLUTION  OF  LIFE 


PL  A  CE: 


NEW  YORK 


DA  TE: 


1918 


COLUMBIA  UNIVERSITY  LIBRARIES 
PRESERVATION  DEPARTMENT 

RIRT  TOHR  APHTC  MICROFORM  i  ARGET 


Original  Material  as  Filmed  -  Existing  Bibliographic  Record 


fphilosophy 
tt)575 


1  D675 
I  0814 

i  abn' 

D575 


Restrictions  on  Use: 


Osborn,  Henry  rairfield,  1857^935  . 

Tl.e  origin  and  evolution  of  life  on  tl,e  theory  o|  action, 

ner's  sons,  i^tfr    1918.  ,^  ,     , 

'  •  ..       .     J-       ,     ^-xx'^      (Half-title:  Hale 


Bibliography :  p.  29:^306^  p^^n,        19 18, 

Copy   ir   /-.ooio-y  i^tr    *-i' <, 

1    Evolution.    2.  I/ifc.  Oripin  of. 

Cow  in  Medical  Library,  ^^^^^g 


17-25802 


rirP^eolocy  Wr^^^^^S  Room.       1918. 


Copy  irl.'GeS^ocy 

vrieht    A 


Copyright    A  473938 


^i 


Master  Negative  # 


'...« 


TECHNICAL  MICROFORM  DATA 
REDUCTION     RATIO:       U?( 


FILM     SiZE:_. 

IMAGE  PLACEMENT:    lA     IIA     IB     IIB 

DATE     FILMED: ^trBj5_^___     INITIALS S__^. 

FILMED  B^:    RESEARCH  PUBLICATIONS.  INC  WOODBRIDGE,  CT 


r 


Association  for  Information  and  Image  Management 

1100  Wayne  Avenue.  Suite  1100 
Silver  Spring,  Maryland  20910 

301/587-8202 


Centimeter 

12        3        4 

ii|ii"ii"['i'!'l"i'h'h'i" 


4 


Inches 


m 


iiiiliiiiliiiili 
I  I    I  I  I 


10       11        12       13       14       15    mm 


1.0 


I.I 


1.25 


50 

■  36 


1.4 


2.5 
2.2 

2.0 


1.8 


1.6 


MPINUFfiCTURED   TO   PIIM   STRNDPRDS 
BY   PPPLIED   IMPGE,     INC. 


i-  '-mi 


if<^ 


1 


30..^ 


»»^ 


,.:^""^    HENRidHi 

iilBiDSBORNiiiil*' 

*«i 

:-l-.-.-.v.-.-.-.-- v.-^><x>-:.:---:':-2  :X .'■ 
■■■>:->i->"-v-:  :•:-•':  K::r;x"  >>:- 

^  I 


^^^->>>:■:^■ 


■!?»>< 


^ip^'^^s^lgi^fiUiw^Si^'y^ 


o 


I 


/ 


/ 


Qs\? 


"-"(\iV  ^c^'iiSM^  JjJ)X 

pftitQsopfiijwSlEms 

CONtrM|tdFFICll 
-S-ETBENiflVENDU. 
%DlSCIPlllNAMrf:^ 


>  is=r 


\      «-^_ -^ y^*^  "~'-_ 


\ 


\^m 


I )] 


*" 


THE  ORIGIN  AND 
EVOLUTION    OF    LIFE 

ON   THE   THEORY   OF   ACTION 
REACTION    AND    INTERACTION    OF    ENERGY 


HALE    LECTURES    OF   THE    NATIONAL   ACADEMY   OF 
SCIENCES,  WASHINGTON,  APRIL,   1916 


n 


t 


il'       ,H!(. 


'%    K,J 


»* »     « >?^  In 


u 


Tyrannosaunts  rex,  the  King  of  the  Tyrant  Saurians. 
The  climax  among  carnivorous  reptiles  of  a  complex  mechanism  for  the 
capture,  storage,  and  release  of  energy.      Contemporary  with  and  de- 
stroyer of  the  large  herbivorous  dinosaurs.     Compare  p.  224. 


THE  ORIGIN  AND 
EVOLUTION  OF  LIFE 


ON   THE   THEORY   OF   ACTION 
REACTION   AND   INTERACTION   OF   ENERGY 


BY 

HENRY   FAIRFIELD   OSBORN 

SCD.  PRINCETON,  HON.  LL.D.  TRIMTY,  PRINCETON,  COLUMBIA,  HON.  D.SC.  CAMBRIDGE 

HON.   PH.D.   CHRISTIANIA 

RESEARCH  PROFESSOR   OF  ZOOLOGY,  COLUMBIA  UNIVERSITY 

VERTEBRATE    PALiEONTOLOGIST    U.    S.    GEOLOGICAL    SURVEY,    CURATOR    EMERITUS    OF   VERTEBRATE 

PALEONTOLOGY   IN   THE   AMERICAN   MUSEUM   OF   NATURAL  HISTORY 

AUTHOR  OF   "from  THE   GREEKS  TO  DARWIN " 
"the   age   of  mammals,"   "men   of  the   old  STONE  AGE" 


WITH    136    ILLUSTRATIONS 


NEW  YORK 
CHARLES   SCRIBNER^S   SONS 

1918 


Copyright,  191 6,  by 
THE   SCIENCE   PRESS 


Copyright,  191 7,  by 
CHARLES  SCRIBNER'S  SONS 


Published  September,  191 7 

Reprinted  November,  December,  191 7 
April,  1918 


<n    - 

r 


i 


I 


' 


P- 


DEDICATED   TO 
MY     COLLEAGUE     AND     FRIEND 

GEORGE  ELLERY  HALE 

head  of  the  mount  wilson  observatory  of  the  carnegie 

institution;  ardent  advocate  of 

the  synthesis  of  the  sciences  in  research 


PREFACE 


4 


In  these  lectures  we  may  take  some  of  the  initial  steps 
toward  an  energy  conception  of  Evolution  and  an  energy 
conception  of  Heredity  and  away  from  the  matter  and  form 
conceptions  which  have  prevailed  for  over  a  century. 

The  first  half  of  this  volume  is  therefore  devoted  to  what 
we  know  of  the  capture,  storage,  release,  and  reproduction  of 
energy  in  its  simplest  and  most  elementary  Hving  phases; 
the  second  half  is  devoted  to  the  evolution  of  matter  and 
form  in  plants  and  animals,  also  interpreted  largely  in  terms 
of  energy  and  mechanics.  Lest  the  reader  imagine  that 
through  the  energy  conception  I  am  at  present  even  pretend- 
ing to  offer  an  explanation  of  the  miracles  of  adaptation  and 
of  heredity,  some  of  these  miracles  are  recited  in  the  second 
part  of  this  volume  to  show  that  the  germ  evolution  is  the 
most  incomprehensible  phenomenon  which  has  yet  been  dis- 
covered in  the  universe,  for  the  greater  part  of  what  we  see  in 
animal  and  plant  forms  is  only  the  visible  expression  of  the  in- 
visible evolution  of  the  heredity-germ. 

We  are  not  ready  for  a  clearly  developed  energy  conception 
of  the  origin  of  life,  still  less  of  evolution  and  of  heredity;  yet 
we  believe  our  theory  of  the  actions,  reactions,  and  interactions 
of  living  energy  will  prove  ^  to  be  a  step  in  the  right  direction. 

It  is  true  that  in  the  organism  itself,  apart  from  the 
heredity-germ,  we  have  made  great  advances^  in  the  energy 

» Some  of  the  reasons  for  this  assertion  are  presented  in  the  successive  chapters  of 
this  volume  and  summarized  in  the  Conclusion. 

2  One  of  the  most  influential  works  in  this  direction  is  Jacques  Loeb's  Dynamics  of 
Living  Matter,  a  synthesis  of  many  years  of  physicochemical  research  on  the  actions  and 
reactions  of  living  organisms.  See  also  Loeb's  more  recent  work,  The  Organism  as  a 
Whole,  published  since  these  lectures  were  written. 

vii 


VUl 


PREFACE 


PREFACE 


IX 


conception.  We  observe  many  of  the  means  by  which  energy 
is  stored,  and  some  of  the  complicated  methods  by  which  it 
is  captured,  protected,  and  released.  We  shall  see  that  highly 
evolved  organisms,  such  as  the  large  reptiles  and  mammals 
and  man,  present  to  the  eye  of  the  anatomist  and  physiologist 
an  inconceivable  complexity  of  energy  and  form;  but  this  we 
may  in  part  resolve  by  reading  the  pages  of  this  volume  back- 
ward, Chinese  fashion,  from  the  mammaP  to  the  monad,  in 
which  we  reach  a  stage  of  relative  simplicity.  Thus  the  or- 
ganism as  an  arena  for  energy  and  matter,  as  a  complex  of  in- 
tricate actions,  becomes  in  a  measure  conceivable.  The 
heredity-germ,  on  the  contrary,  remains  inconceivable  in  each 
of  its  three  powers,  namely,  in  the  Organism  which  it  produces, 
in  the  succession  of  germs  to  which  it  gives  rise,  and  in  its  own 
evolution  in  course  of  time. 

Having  now  stated  the  main  object  of  these  lectures,  I 
invite  the  reader  to  study  the  following  pages  with  care,  be- 
cause they  review  some  of  the  past  history  and  introduce  some 
of  the  new  spirit  and  purpose  of  the  search  for  causes  in  the 
domain  of  energy.  I  begin  with  matters  which  are  well  known 
to  all  biologists  and  proceed  to  matters  which  are  somewhat 
more  difficult  to  understand  and  more  novel  in  purpose. 

In  this  review  we  need  not  devote  any  time  or  space  to 
fresh  arguments  for  the  truth  of  evolution.  The  demonstra- 
tion of  evolution  as  a  universal  law  of  living  nature  is  the 
great  intellectual  achievement  of  the  nineteenth  century. 
Evolution  has  outgrown  the  rank  of  a  theory,  for  it  has  won 
a  place  in  natural  law  beside  Newton's  law  of  gravitation, 
and  in  one  sense  holds  a  still  higher  rank,  because  evolution  is 
the  universal  master,  while  gravitation  is  one  among  its  many 

^  Man  is  not  treated  at  all  in  this  volume,  the  subject  being  reserved  for  the  final 
lectures  in  the  Hale  Series. 


agents.  Nor  is  the  law  of  evolution  any  longer  to  be  associ- 
ated with  any  single  name,  not  even  with  that  of  Darwin, 
who  was  its  greatest  exponent.^  It  is  natural  that  evolution 
and  Darwinism  should  be  closely  connected  in  many  minds, 
but  we  must  keep  clear  the  distinction  that  evolution  is  a  law, 
while  Darwinism  is  merely  one  of  the  several  ways  of  inter- 
preting the  workings  of  this  law. 

In  contrast  to  the  unity  of  opinion  on  the  law  of  evolution 
is  the  wide  diversity  of  opinion  on  the  causes  of  evolution. 
In  fact,  the  causes  of  the  evolution  of  life  are  as  mysterious  as 
the  law  of  evolution  is  certain.  Some  contend  that  we  already 
know  the  chief  causes  of  evolution,  others  contend  that  we 
know  little  or  nothing  of  them.  In  this  open  court  of  con- 
jecture, of  hypothesis,  of  more  or  less  heated  controversy,  the 
great  names  of  Lamarck,  of  Darwin,  of  Weismann  figure  promi- 
nently as  leaders  of  different  schools  of  opinion;  while  there 
are  others,  like  myself,^  who  for  various  reasons  belong  to  no 
school,  and  are  as  agnostic  about  Lamarckism  as  they  are 
about  Darwinism  or  Weismannism,  or  the  more  recent  form 
of  Darwinism,  termed  Mutation  by  de  Vries. 

In  truth,  from  the  period  of  the  earliest  stages  of  Greek 
thought  man  has  been  eager  to  discover  some  natural  cause  of 
evolution,  and  to  abandon  the  idea  of  supernatural  interven- 
tion in  the  order  of  nature.  Between  the  appearance  of  The 
Origin  oj  Species,  in  1859,  and  the  present  time  there  have 
been  great  waves  of  faith  in  one  explanation  and  then  in  an- 
other: each  of  these  waves  of  confidence  has  ended  in  disap- 
pointment, until  finally  we  have  reached  a  stage  of  very  general 

1  See  From  the  Greeks  to  Darwin  (Macmillan  &  Co.,  1894),  by  the  present  author,  in 
which  the  whole  history  of  the  evolution  idea  is  traced  from  its  first  conception  down  to 

the  time  of  Darwin. 

*  Osbom,  H.  F.,  "The  Hereditary  Mechanism  and  the  Search  for  the  Unknown  Factors 
of  Evolution,"  The  Amer.  Naturalist,  May,  1895,  pp.  418-439. 


\ 


PREFACE 


PREFACE 


XI 


scepticism.  Thus  the  long  period  of  observation,  experiment, 
and  reasoning  which  began  with  the  French  natural  philosopher 
Buffon,  one  hundred  and  fifty  years  ago,  ends  in  1916  with  the 
general  feeling  that  our  search  for  causes,  far  from  being  near 
completion,  has  only  just  begun. 

Our  present  state  of  opinion  is  this:  we  know  to  some 
extent  how  plants  and  animals  and  man  evolve;  we  do  not 
know  why  they  evolve.  We  know,  for  example,  that  there 
has  existed  a  more  or  less  complete  chain  of  beings  from  monad 
to  man,  that  the  one-toed  horse  had  a  four-toed  ancestor,  that 
man  has  descended  from  an  unknown  ape-like  form  somewhere 
in  the  Tertiary.  We  know  not  only  those  larger  chains  of 
descent,  but  many  of  the  minute  details  of  these  transforma- 
tions. We  do  not  know  their  internal  causes,  for  none  of  the 
explanations  which  have  in  turn  been  offered  during  the  last 
hundred  years  satisfies  the  demands  of  observation,  of  experi- 
ment, of  reason.  It  is  best  frankly  to  acknowledge  that  the 
chief  causes  of  the  orderly  evolution  of  the  germ  are  still  en- 
tirely unknown,  and  that  our  search  must  take  an  entirely 
fresh  start. 

As  regards  the  continuous  adaptability  and  fitness  of  liv- 
ing things,  we  have  a  reasonable  interpretation  of  the  causes 
of  some  of  the  phenomena  of  adaptation,  but  they  are  the 
smaller  part  of  the  whole.  Especially  mysterious  are  the  chief 
phenomena  of  adaptation  in  the  germ;  the  marvellous  and 
continuous  fitness  and  beauty  of  form  and  function  remain 
largely  unaccounted  for.  We  have  no  scientific  explana- 
tion for  those  processes  of  development  from  within,  which 
Bergson^  has  termed  'devolution  creatrice,"  and  for  which 
Driesch-   has   abandoned  a  natural  explanation  and  assumed 

^  Bergson,  Henri,  1907,  U Evolution  Creatrice. 

'Driesch,  Hans,  1908,  The  Science  and  Philosophy  of  the  Organism. 


'I 


the  existence  of  an  entelechy,  that  is,  an  internal  perfecting 
influence. 

This  confession  of  failure  is  part  of  the  essential  honesty  of 
scientific  thought.  We  recall  the  fact  that  our  baffled  state 
of  mind  is  by  no  means  new,  for  in  Kant's  work  of  1790,  his 
Methodical  System  of  the  Teleological  Faculty  of  Judgment^  he 
divides  all  things  in  nature  into  the  '^ inorganic, "  in  which 
natural  causes  prevail,  and  the  '^ organic,''  in  which  the  active 
teleological  (i.  e,,  purposive)  principle  of  adaptation  is  sup- 
posed to  prevail.  There  was  in  Kant's  mind  a  cleft  between 
the  domain  of  primeval  matter  and  the  domain  of  life,  for  in 
the  latter  he  assumes  the  presence  of  a  supernatural  principle, 
of  final  causes  acting  toward  definite  ends.  This  view  is  ex- 
pressed in  his  Teleological  Faculty  of  Judgment  as  follows : 

'*But  he"  (the  archaeologist  of  Nature)  ''must  for  this  end 
ascribe  to  the  common  mother  an  organization  ordained  pur- 
posely with  a  view  to  the  needs  of  all  her  offspring,  otherwise 
the  possibility  of  suitability  of  form  in  the  products  of  the 
animal  and  vegetable  kingdoms  cannot  be  conceived  at  all."^ 

"It  is  quite  certain  that  we  cannot  become  sufficiently 
acquainted  with  organized  creatures  and  their  hidden  poten- 
tialities by  aid  of  purely  mechanical  natural  principles;  much 
less  can  we  explain  them;  and  this  is  so  certain,  that  we  may 
boldly  assert  that  it  is  absurd  for  man  even  to  conceive  such 
an  idea,  or  to  hope  that  a  Newton  may  one  day  arise  able  to 
make  the  production  of  a  blade  of  grass  comprehensible,  ac- 
cording to  natural  laws  ordained  by  no  intention;  such  an 
insight  we  must  absolutely  deny  to  man."^ 

For  a  long  period  after  The  Origin  of  Species  appeared, 
Haeckel  and  many  others  believed  that  Darwin  had  arisen 
as  the  Newton  for  whom  Kant  did  not  dare  to  hope;  but  no 

*  Kant,  Emmanuel,  1 790,  §  79.  2  /^j</.^  §  7^, 


•  • 

xu 


PREFACE 


PREFACE 


Xlll 


/ 


one  now  claims  for  Darwin's  law  of  natural  selection  a  rank 
equal  to  that  of  Newton's  law  of  gravitation. 

If  we  admit  the  possibility  that  Kant  was  right,  and  that 
we  can  never  become  sufficiently  acquainted  with  organized 
creatures  and  their  hidden  potentialities  by  aid  of  purely 
natural  principles,  we  may  be  compelled  to  regard  the  origin 
and  evolution  of  life  as  an  ultimate  law  like  the  law  of  gravita- 
tion, which  may  be  mathematically  and  physically  defined, 
but  cannot  be  resolved  into  any  causes.  We  are  not  wilHng, 
however,  to  make  such  an  admission  at  the  present  time  and 
to  abandon  the  search  for  causes. 

The  question  then  arises,  why  has  our  long  and  arduous 
search  after  the  causes  of  evolution  so  far  been  unsuccessful? 
One  reason  why  our  search  may  have  failed  appears  to  be  that 
the  chief  explorers  have  been  trained  in  one  school  of  thought, 
namely,  the  school  of  the  naturalist.     They  all  began  their  studies 
with  observations  on  the  external  form  and  color  of  animals 
and  plants;    they  have  all  observed  the  end  results  of  long 
processes  of  evolution.     Buffon  derived  his  ideas  of  the  causes 
of  evolution  from  the  comparison  of  the  wild  and  domestic 
animals  of  the  Old  and  New  Worlds;  Goethe  observed  the  com- 
parative anatomy  of  man  and  of  the  higher  animals;  Lamarck 
observed  the  higher  phases  of  the  vertebrate  and  invertebrate 
animals;  Darwin  observed  the  form  of  most  of  the  domestic 
animals  and  cultivated  plants  and,  finally,  of  man,  and  noted 
the  adaptive  significance  of  the  colors  of  flowers  and  birds, 
and  the  relations  of  flowers  with  birds  and  insects;  de  Vries 
compared  the  wild  and  cultivated  species  of  plants.     Thus  all 
the  great  naturaUsts  in  turn— Buffon,  Goethe,  Lamarck,  Dar- 
win, and  de  Vries— have  attempted  to  reason  backward,  as  it 
were,  from  the  highly  organized  appearances  of  form  and  color 
to   their   causes.     The   same   is   true   of   the  palaeontologists: 


{ 


\ 


i 


Cope  turned  from  the  form  of  the  teeth  and  skeleton  backward 
to  considerations  of  cause  and  energy,  Osborn^  reached  a  con- 
ception of  evolution  as  of  the  relations  of  fourfold  form,  and 
hence  proposed  the  word  tetraplasy. 

The  Heredity  theories  of  Darwin,  of  de  Vries,  of  Weis- 
mann  have  also  been  largely  in  the  material  conceptions  of 
fine  particles  of  matter  such  as  *'pangens"  and  '* determinants." 
There  has  been  some  consideration  of  function  and  of  the 
internal  phenomena  of  organisms,  but  there  has  been  little 
or  no  serious  attempt  to  reverse  the  mental  processes  of  the 
naturalist  and  substitute  those  of  the  physicist  in  considering 
the  causes  of  evolution. ^ 

Moreover,  all  the  explanations  of  evolution  which  have\^ 
been  offered  by  three  generations  of  naturalists  align  themselves 
under  two  main  ideas  only.  The  first  is  the  idea  that  the 
causes  of  evolution  are  chiefly  from  without  inward,  namely, 
beginning  in  the  environment  of  the  body  and  extending  into 
the  germ:  this  idea  is  centripetal.  The  second  idea  is  just  the 
reverse:  it  is  centrifugal,  namely,  that  the  causes  begin  in  the 
germ  and  extend  outward  into  the  body  and  into  the  environ-^ 

ment. 

The  pioneer  of  the  first  order  of  ideas  is  Buffon,  who  early  \ 
reached  the  opinion  that  favorable  or  unfavorable  changes 
of  environment  directly  alter  the  hereditary  form  of  succeed- 
ing generations.  Lamarck,^  the  founder  of  a  broader  and 
more  modern  conception  of  evolution,  concluded  that  the 
changes  of  form  and  function  in  the  body  and  nervous  system 
induced  by  habit  and  environment  accumulate  in  the  germ, 

*  Osbom,  H.  F.,  "Tetraplasy,  the  Law  of  the  Four  Inseparable  Factors  of  Evolution," 
Jour.  Acad.  Nat.  Sci.  Phila.,  special  anniversary  volume  issued  September  14,  1912,  pp. 

275-309- 

*  See  fuller  exposition  on  pp.  10-23  of  this  volume. 

»  For  a  fuller  exposition  of  the  theory  of  Lamarck,  see  pp.  143,  144. 


xiv 


PREFACE 


PREFACE 


XV 


and  are  handed  on  by  heredity  to  succeeding  generations. 
This  essential  idea  of  Lamarckism  was  refined  and  extended 
by  Herbert  Spencer,  by  Darwin  himself,  by  Cope  and  many 
others;  but  it  has  thus  far  failed  of  the  crucial  test  of  observa- 
tion and  experiment,  and  has  far  fewer  adherents  to-day  than 

it  had  forty  years  ago. 

We  now  perceive  that  Darwin's  original  thought  turned 
to  the  opposite  idea,  namely,  to  sudden  changes  in  the  heredity- 
germ  itself^  as  giving  rise  spontaneously  to  more  or  less  adap- 
tive changes  of  body  form  and  function  which,  if  favorable  to 
survival,  might  be  preserved  and  accumulated  through  natural 
selection.  This  pure  Darwinism  has  been  refined  and  extended 
by  Wallace,  Weismann,  and  especially  of  late  by  de  Vries, 
whose  ''mutation  theory"  is  pure  Darwinism  in  a  new  guise. 

Weismann's  great  contribution  to  thought  has  been  to 
point  out  the  very  sharp  distinction  which  undoubtedly  exists 
between  the  hereditary  forces  and  predispositions  in  the  hered- 
ity-germ and  the  visible  expression  of  these  forces  in  the  or- 
ganism. It  is  in  the  ''germ-plasm,''  as  Weismann  terms  it— 
in  this  volume  termed  the  '^heredity-chromatin"— that  the  real 
evolution  of  all  predispositions  to  form  and  function  is  taking 
place,  and  the  problem  of  causes  of  evolution  has  become  an 
infinitely  more  difficult  one  since  Weismann  has  compelled  us 
to  reaHze  that  the  essential  question  is  the  causes  of  germinal 
evolution  rather  than  the  causes  of  bodily  evolution  or  of  en- 
vironmental evolution. 

Again,  despite  the  powerful  advocacy  of  pure  Darwinism 
by  Weismann  and  de  Vries  in  the  new  turn  that  has  been 
given  to  our  search  for  causes  by  the  rediscovery  of  the  law  of 
Mendel  and  the  heredity  doctrines  which  group  under  Men- 

1  Osborn,  H.  F.,  "Darwin's  Theory  of  F.volution  by  the  Selection  of  Minor  Saltations," 
The  Amer.  Naturalist,  February,  191 2,  pp.  76-82. 


\\ 


J 


I 


I 


DELISM,^  it  may  be  said  that  Darwin's  law  of  selection  as  a 
natural  explanation  of  the  origin  of  all  fitness  in  form  and  func- 
tion has  also  lost  its  prestige  at  the  present  time,  and  all  of 
Darwinism  which  now  meets  with  universal  acceptance  is  the 
law  of  the  survival  of  the  fittest,  a  Hmited  appHcation  of  Darwin's 
great  idea  as  expressed  by  Herbert  Spencer.  Few  biologists 
to-day  question  the  simple  principle  that  the  fittest  tend  to 
survive,  that  the  unfit  tend  to  be  eliminated,  and  that  the 
present  aspect  of  the  entire  living  world  is  due  to  this  great 
pruning-knife  which  is  constantly  sparing  those  which  are  best 
fitted  or  adapted  to  any  conditions  of  environment  and  cutting 
out  those  which  are  less  adaptive.  But  as  Cope  pointed  out, 
the  survival  of  fitness  and  the  origin  of  fitness  are  two  very^ 
different  phenomena. 

If  the  naturalists  have  failed  to  make  progress  in  the  search 
for  causes,  I  believe  it  is  chiefly  because  they  have  attempted 
to  reason  backward  from  highly  complex  plant  and  animal 
forms  to  causes.  The  cart  has  always  been  placed  before  the 
horse;  or,  to  express  it  in  another  way,  thought  has  turned 
from  \ht  forms  of  living  matter  toward  a  problem  which  involves 
the  phenomena  of  living  energy;  or,  still  more  briefly,  we  have 
been  thinking  from  matter  backward  into  energy  rather  than 
from  energy  forward  into  matter  and  form. 

All  speculation  on  the  origin  of  Hfe,  fruitless  as  it  may  at 
first  appear,  has  the  advantage  that  it  compels  a  sudden  re- 
versal of  the  naturaUst's  point  of  view,  for  we  are  forced  to 
work  from  energy  upward  into  form,  because,  at  the  begin- 
ning, form  is  nothing,  energy  is  everything.  Energy  appears 
to  be  the  chief  end  of  life— the  first  efforts  of  life  work  toward 
the  capture  of  energy,  the  storage  of  energy,  the  release  of 

» Mendelism  chiefly  refers  to  the  distinction  and  laws  of  distribution  of  separable  or 
unit  characters  in  the  germ  and  in  the  individual  in  course  of  its  development. 


XVI 


PREFACE 


energy.     The  earliest  adaptations  we  know  of  are  designed  for 
the  capture  and  storage  of  energy. 

Matter  in  the  state  of  relative  rest  known  as  plant  and 
animal  form  is  present,  but,  in  the  simplest  and  lowUest  types 
of  life,  form  does  not  conceal  and  mask  the  processes  of  energy 
as  it  does  in  the  higher  types.  Similarly,  the  earhest  fitness 
we  discover  in  the  bacteria  or  monads  is  the  fitness  of  group- 
ing and  organizing  different  kinds  of  energy— the  energy  of 
molecules,  of  atoms,  of  electrons  as  displayed  in  the  twenty- 
six  or  more  chemical  elements  which  enter  into  life. 

In  searching  among  these  early  episodes  of  life  in  its  origin 
we  discover  that  four  complexes  of  energy  are  successively 
added  and  combined.     The  Inorganic  Environment  of  the  sun, 
of  the  earth,  of  the  water,  of  the  atmosphere  is  exploited  thor- 
oughly in  search  of  energy  by  the  Organism:   the  organism 
itself  becomes  an  organism  only  by  utiHzing  the  energy  of  the 
environment  and  by  coordinating  its  own  internal  energies. 
Whether  the  Germ  as  the  special  centre  of  heredity  and  repro- 
duction of  energy  is  as   ancient  as  the  organism   we  do  not 
know;  but  we  do  know  that  it  becomes  a  distinct  and  highly 
complex  centre  of  potential  energy  which  directs  the  way  to 
the  entire  energy  complex  of  the  newly  developing  organism. 
Finally,  as  organisms  multiply  and  acquire  various  kinds  of 
energy,  the  Life  Environment  arises  as  a  new  factor  in  the 
energy  complex.     Thus  in  the  process  of  the  origin  and  early 
evolution  of  life,  complexes  of  four  greater  and  lesser  energy 
groups  arise,  namely:  inorganic  environment:  the  energy 
content  in  the  sun,  the  earth,  the  water,  and  the  air;  organism: 
the  energy  of  the  individual,  developing  and  changing  the  cells 
and  tissues  of  the  body,  including  that  part  of  the  germ  which 
enters  every  cell;  heredity-germ:  the  energies  of  the  heredity 
substance  (heredity-chromatin)  concentrated  in  the  reproduc- 


PREFACE 


xvu 


tive  cells  of  continuous  and  successive  generations,  as  well  as 
in  all  the  cells  and  tissues  of  the  organism;  and  life  environ- 
ment :  beginning  with  the  monads  and  algae  and  ascending  in  a 
developing  scale  of  plants  and  animals. 

There  are  here  Jour  evolutions  of  energy  rather  than  one, 
and  the  problem  of  causes  is  how  the  four  evolutions  are  ad- 
justed to  each  other;  and  especially  how  the  evolution  of  the 
germ  adjusts  itself  to  that  of  the  inorganic  environment  and 
of  the  life  environment,  and  to  the  temporary  evolution  of  the 

organism  itself. 

I  do  not  propose  to  evade  the  difficulties  of  the  problem 
of  the  origin  and  evolution  of  life  by  minimizing  any  of  them. 

Whether  our  approach  through  energy  will  lead  to  the  dis- 
covery of  some  at  least  of  the  unknown  causes  of  evolution 
remains  to  be  determined  by  many  years  of  observation  and 
experiment.     Whereas  our  increasing  knowledge  of  energy  in 
matter  reveals  an  infinity  of  energized  particles  even  in  the  in- 
finitely minute  aggregations  known  as  molecules— an  infinity 
which  we  observe  but  do  not  comprehend— we  find  in  our 
search  for  causes  of  the  origin  and  evolution  of  life  that  we  have 
reached  an  entirely  new  point  of  departure,  namely,  that  of 
the  physicist  and  chemist  rather  than  the  old  point  of  departure 
of  the  naturalist.     We  have  obtained  a  starting-point  for  new 
and  untried  paths  of  exploration  which  may  be  followed  dur- 
ing the  present  century— paths  which  have  long  been  trodden 
with  a  different  purpose  by  physicists  and  chemists,  and  by 
physiologists  and  biochemists  in  the  study  of  the  organism  it- 
self. 


The  reader  may  thus  follow,  step  by  step,  my  own  experi- 
ence and  development  of  thought  in  preparing  these  lectures. 
The  reason  why  I  happened  to  begin  this  volume  with  the  prob- 


xvm 


PREFACE 


lem  of  energy  and  end  with  that  of  the  evolution  of  form  is 
that  these  lectures  were  prepared  and  dehvered  midway  in  a 
cosmic-evolution  series  which  opened  with  Sir  Ernest  Ruther- 
ford's^  discourse  on  ''The  Constitution  of  Matter  and  the 
Evolution  of  the  Elements/'  and  continued  with  ''The  Evolu- 
tion of  the  Stars  and  the  Formation  of  the  Earth,"  by  Doctor 
William  Wallace  Campbell,-  and  "The  Evolution  of  the  Earth," 
by  Professor  Thomas  Chrowder  Chamberlin.^  My  friend 
George  Ellery  Hale  placed  upon  me  the  responsibiUty  of 
weaving  the  partly  known  and  still  more  largely  unknown 
narrative  which  connects  the  forms  of  energy  and  matter  ob- 
served in  the  sun  and  stars  with  the  forms  of  energy  and  matter 
which  we  observe  in  the  bodies  of  our  own  mammalian  ances- 
tors. Certainly  we  appear  to  inherit  some,  if  not  all,  of  our 
physicochemical  characters  from  the  sun;  and  to  this  degree 
we  may  claim  kinship  with  the  stellar  universe.  Some  of  our 
distinctive  characters  and  functions  are  actually  properties  of 
our  ancestral  star.  Physically  and  chemically  we  are  the  off- 
spring of  our  great  luminary,  which  certainly  contributes  to 
us  all  our  chemical  elements  and  all  the  physical  properties 
which  bind  them  together. 

Some  day  a  constellation  of  genius  will  unite  in  one  labora- 
tory on  the  life  problem.  This  not  being  possible  at  present, 
I  have  endeavored  during  the  past  two  years^  for  the  purposes 

1  Rutherford,  Sir  Ernest,  "The  Constitution  of  Matter  and  the  Evolution  of  the 
Elements,"  first  series  of  lectures  on  the  William  Ellery  Hale  foundation,  delivered  in 
April,  1914;  Pop.  Sci.  Man.,  August,  1915,  pp.  105-142. 

2  Campbell,  William  Wallace,  "The  Evolution  of  the  Stars  and  the  Formation  of  the 
Earth,"  second  series  of  lectures  on  the  William  Ellery  Hale  foundation,  delivered  De- 
cember 7  and  8,  1914;  Pop.  Sci.  Mon.,  September,  1915,  pp.  209-235;  Scientific  Monthly, 
October,  1915,  pp.  1-17;  November,  1915,  pp.  177-194;  December,  1915,  pp.  238-255. 

3  Chamberlin,  Thomas  Chrowder,  "The  Evolution  of  the  Earth,"  third  series  of  lec- 
tures on  the  William  F^Uery  Hale  foundation,  delivered  April  19-21,  191 5;  Scientific 
Monthly,  May,  1916,  pp.  417-437;  June,  1916,  pp.  536-556. 

*  I  first  opened  a  note-book  on  this  subject  in  the  month  of  April,  191 5,  when  I  was 
invited  by  Doctor  George  Ellery  Hale  to  undertake  the  preparation  of  these  lectures. 


PREFACE 


XIX 


of  my  own  task  to  draw  a  large  number  of  speciaHsts  together 
in  correspondence  and  in  a  series  of  personal  conferences  and 
discussions;  and  whatever  merits  this  volume  may  possess  are 
partly  due  to  their  generous  response  in  time  and  thought  to 
my  invitation.  Their  suggestions  are  duly  acknowledged  in 
footnotes  throughout  the  text.  I  have  myself  approached  the 
problem  through  a  synthesis  of  astronomy,  geology,  physics, 
chemistry,  and  biology. 

In  consulting  authorities  on  this  subject  I  have  made  one 
exception,  namely,  the  problem  of  the  origin  of  life  itself  with 
its  vast  literature  going  back  to  the  ancients — I  have  read  none 
of  it  and  quoted  none  of  it.  In  order  to  consider  the  problem 
from  a  fresh  and  unbiassed  point  of  view,  I  have  also  purposely 
refrained  from  reading  any  of  the  recent  and  authoritative 
treatises  of  Schafer,^  Moore,-  and  others  on  the  origin  of  hfe. 
It  will  be  interesting  for  the  reader  to  compare  the  conclusions 
previously  reached  by  these  distinguished  chemists  with  those 
presented  in  the  following  pages. 

For  invaluable  guidance  in  the  phenomena  of  physics  I 
am  deeply  indebted  to  my  colleague  Professor  Michael  I. 
Pupin,  of  Columbia  University,  who  has  given  me  his  views 
as  to  the  fundamental  relation  of  Newton's  laws  of  motion  to 
the  modern  laws  of  heat  and  energy  (thermodynamics),  and  has 
clarified  the  laws  of  action,  reaction,  and  interaction  from  the 
physical  standpoint.  Without  this  aid  I  could  never  have 
developed  what  I  believe  to  be  the  new  biological  principle  set 
forth  in  this  work.  I  owe  to  him  the  confirmation  of  the  use 
of  the  word  interaction  as  a  physical  term,  which  had  occurred 
to  me  first  as  a  biological  term. 

*  Schafer,  Sir  Edward  A.,  Life,  Its  Nature,  Origin,  and  Maintenance,  Longmans,  Green 
&  Co.,  New  York,  191 2. 

2  Moore,  Benjamin,  The  Origin  and  Nature  of  Life,  Henry  Holt  &  Co.,  New  York; 
Williams  &  Norgate,  London,  19 13. 


I! 


l! 


iii 


XX 


PREFACE 


As  to  the  physicochemical  actions  and  reactions  of  the 
living  organism  I  have  drawn  especially  from  Loeb's  Dynamics 
of  Living  Matter,  In  the  physicochemical  section  I  am  also 
greatly  indebted  to  the  very  suggestive  work  of  Henderson 
entitled  The  Fitness  of  the  Environment,  from  which  I  have 
especially  derived  the  notion  that  fitness  long  antedates  the 
origin  of  Hfe.  Professor  Hans  Zinsser,  of  Columbia  University, 
has  aided  in  a  review  of  Ehrlich's  theory  of  antibodies  and  the 
results  of  later  research  concerning  them.  Professor  Ulric 
Dahlgren,  of  Princeton  University,  has  aided  the  preparation  of 
this  work  with  valuable  notes  and  suggestions  on  the  light, 
heat,  and  chemical  rays  of  the  sun,  and  on  phosphorescence 
and  electric  phenomena  in  the  higher  organisms. 

In  the  geochemical  and  geophysical  section  I  am  indebted 
to  my  colleagues  in  the  National  Academy,  F.  W.  Clarke  and 
George  F.  Becker,  not  only  for  the  revision  of  parts  of  the 
text,  but  for  many  valuable  suggestions  and  criticisms. 

For  suggestions  as  to  the  chemical  conditions  which  may 
have  prevailed  in  the  earth  during  the  earliest  period  in  the 
origin  of  Ufe,  as  well  as  for  criticisms  and  careful  revision  of 
the  chemical  text  I  am  especially  indebted  to  my  colleague  in 
Columbia  University,  Professor  WiUiam  J.  Gies. 

In  the  astronomic  section  I  desire  to  express  my  indebted- 
ness to  George  Ellery  Hale,  of  the  Mount  Wilson  Observatory, 
for  the  use  of  photographs,  and  to  Henry  Norris  Russell,  of 
Princeton  University,  for  notes  upon  the  heat  of  the  primordial 
earth's  surface.  In  the  early  narrative  of  the  earth's  history 
and  in  the  subsequent  geographic  and  physiographic  charts 
and  maps  Professor  Charles  Schuchert  and  Professor  Joseph 
Barrell,  of  Yale  University,  kindly  cooperated  with  the  loan  of 
illustrations  and  otherwise.  In  the  section  on  the  evolution  of 
bacteria,  which  is  a  part  pertaining  to  the  idea  of  the  early 


PREFACE 


XXI 


r\ 


evolution  of  energy  in  Hving  matter,  I  enjoyed  the  cooperation 
of  Doctor  I.  J.  Kligler,  formerly  of  the  American  Museum  of 
Natural  History,  and  now  at  the  Rockefeller  Institute  for 
Medical  Research. 

In  the  botanical  section  I  am  especially  indebted  to  Pro- 
fessor T.  H.  Goodspeed,  of  the  University  of  CaHfornia,  and  to 
Doctor  Marshall  Avery  Howe,  of  the  Botanical  Gardens,  for 
many  valuable  notes  and  suggestions,  as  well  as  for  certain 
illustrations.  In  the  early  zoological  section  I  am  indebted 
to  my  colleagues  at  Columbia  University,  Professor  Edmund 
B.  Wilson  and  Professor  Gary  N.  Calkins.  Especial  thanks 
are  due  to  Mr.  Roy  W.  Miner,  of  the  American  Museum,  for  his 
careful  comparisons  of  recent  forms  of  marine  hfe  with  the  Cam- 
brian forms  discovered  by  Doctor  Charles  Walcott,  who  sup- 
pHed  me  with  the  beautiful  photographs  shown  in  Chapter  IV. 

In  preparing  the  chapters  on  the  evolution  of  the  verte- 
brates, I  have  turned  to  my  colleague  Professor  W.  K.  Gregory, 
of  the  American  Museum  and  Columbia  University,  who  has 
aided  both  with  notes  and  suggestions,  and  in  the  supervision 
of  various  illustrations  relating  to  the  evolution  of  vertebrate 
form.  The  illustrations  are  chiefly  from  the  collections  of  the 
American  Museum  of  Natural  History,  as  portrayed  in  original 
drawings  by  Charles  R.  Knight,  Erwin  S.  Christman,  and 
Richard  Deckert.  The  entire  work  has  been  faithfully  collated 
and  put  through  the  press  by  my  research  assistant.  Miss 
Christina  D.  Matthew. 

It  affords  me  great  pleasure  to  dedicate  this  work  to  the 
astronomer  friend  whose  enthusiasm  for  my  own  field  of  work 
in  biolog}^  and  palaeontology  has  always  been  a  source  of  en- 
couragement and  inspiration. 

Henry  Fairfield  Osborn. 

American  Museum  of  Natural  History, 
February  26,  191 7. 


CONTENTS 

INTRODUCTION 

PAGE 

Four  questions  regarding. life i 

The  energy  concept  of  life lo 

The  four  complexes  of  energy i8 


PART   I.     THE   ADAPTATION   OF   ENERGY 

CHAPTER  I 

Preparation  of  the  Earth  for  Life 

The  lifeless  earth 24 

The  lifeless  water 34 

The  atmosphere 39 

CHAPTER  II 

The  Sun  and  the  Physicochemical  Origins  of  Life 

Heat  and  light 43 

Life  elements  in  the  sun 45 

Heat  and  electric  energy 48 

The  capture  of  sunlight 51 

Ionization — the  electric  energy  of  atoms 53 

Coordination  of  activities  by  means  of  interaction      ...  56 

Functions  of  the  chemical  life  elements 59 

Primary  stages  of  life 67 

xxiii 


xxiv  CONTENTS 

PAGE 

New  organic  compounds "9 

Interactions— ENZYMES,  antibodies,  hormones,  and  chalones  .  71 

Chemical  messengers 7  2 

Physicochemical  differentiation 78 

CHAPTER  III 
Energy  Evolution  of  Bacteria,  Alg^,  and  Plants 

Evolution  of  bacteria 

Protoplasm  and  heredity-chromatin 9^ 

Chlorophyll— THE  sunlight  converter  of  plants      ....      99 

Evolution  of  alg.e— the  most  primitive  plants loi 

Plant  and  animal  evolution  contrasted 105 

PART   II.     THE   EVOLUTION   OF  ANIMAL   FORM 

CHAPTER  IV 

The  Origins  of  Animal  Life  and  Evolution  of  the 

Invertebrates 

Evolution  of  Protozoa ^^° 

Evolution  of  Metazoa ^^7 

Cambrian  invertebrates ^^° 

Environmental  changes ^34 

Mutations  of  Waagen ^3^ 

CHAPTER  V 
Visible  and  Invisible  Evolution  of  the  Vertebrates 

Evolution  of  the  germ ^4^ 

Character  evolution ^4o 

The  laws  of  adaptation ^5^ 


CONTENTS 


XXV 


CHAPTER  VI 

Evolution  of  Body  Form  in  the  Fishes  and  Amphibians 

PAGE 

Earliest  known  fishes 160 

Early  armored  fishes 165 

Primordial  sharks 167 

Rise  of  modern  fishes 169 

Evolution  of  the  amphibians 177 

CHAPTER  VII 
Form  Evolution  of  the  Reptiles  and  Birds 

Earliest  reptiles 184 

Mammal-like  reptiles 191 

Adaptive  radiation  of  reptiles 193 

Aquatic  reptiles    . 198 

Carnivorous  dinosaurs 210 

Herbivorous  dinosaurs 216 

'  Flying  reptiles 226 

Origin  of  birds 226 

Arrested  reptilian  evolution 231 

CHAPTER  VIII 

Evolution  of  the  Mammals 

Origin  iOf  mammals 234 

Character  evolution 238 

Causes  of  evolution 245 

Modes  of  evolution 251 


xi 


xxvi  CONTENTS 

PAGE 

Adaptation  to  environment ^53 

Geographic  distribution ^59 

Changes  of  proportion ^^3 

Retrospect  and  prospect ^75 

Conclusion 

APPENDIX 

NOTE 

I.    Different  modes  of  storage  and  release  of  energy  in 

LIVING   organisms ^°5 

II.    Blue-green  alg^  possibly  among  the  first  settlers  of 

OUR  PLANET ^°5 

III.  One  secret  of  life— synthetic  transformation  of  in- 

different material ^°" 

IV.  Interaction    through    catalysis— the    acceleration    of 

CHEMICAL  REACTIONS  THROUGH  THE  PRESENCE  OF  ANOTHER 
SUBSTANCE  WHICH  IS  NOT  CONSUMED  BY  THE  REACTION      286 

V.    The  CAUSES  or  agents  of  speed  and  order  in  the  reac- 
tions OF  living  bodies— enzymes,  colloids,  etc.       .     .     287 

VI.    Interactions  of  the  organs  of  internal  secretion  and 

HEREDITY ^^ 

VII.    Table— RELATIONS  of  the  principal  groups  of  animals 

REFERRED   TO   IN   THE   TFXT ^QO 

Bibliography ^93 

Index 3^7 


ILLUSTRATIONS 


Plate.     Tyrannosaurus  rex,  the  "king  of  the  tyrant  saurians"  .      .  Frontispiece 

FIG.  PAGE 

1.  The  moon's  surface 30 

2.  Deep-sea  ooze,  the  foraminifera 32 

3.  Light,  heat,  and  chemical  influence  of  the  sun 44 

4.  Chemical  life  elements  in  the  sun 46 

5.  The  earliest  phyla  of  plant  and  animal  life 50 

6.  Hydrogen  vapor  in  the  solar  atmosphere 60 

7.  Hydrogen  flocculi  surrounding  sun-spots 61 

8.  The  sun,  showing  sun-spots  and  calcium  vapor 64 

9.  Chemical  life  elements  in  the  sun 65 

10.  Hand  form,  determined  by  heredity  and  secretions 76 

11.  Fossil  and  living  bacteria  compared 85 

12.  Protoplasm  and  chromatin  of  .Iw^ftd 93 

13.  The  two  structural  components  of  the  living  world 94 

14.  Chromatin  in  Sequoia  and  Trillium  compared 96 

15.  Fossil  and  living  algai  compared 102 

16.  Typical  forms  of  Protozoa 112 

17.  Light,  heat,  and  chemical  influence  of  the  sun 113 

18.  Skeletons  of  typical  Protozoa 115 

19.  Map — Late  Lower  Cambrian  world  environment 119 

20.  A  Mid-Cambrian  trilobite 121 

21.  Brachiopods,  Cambrian  and  recent 123 

22.  Horseshoe  crab  and  shrimp,  Cambrian  and  recent 124 

23.  Map — Middle  Cambrian  world  environment 125 

24.  Sea-cucumbers,  Cambrian  and  recent 127 

xxvii 


1 


xxviii  ILLUSTRATIONS 

PAGE 

no. 

25.  Worms,  Middle  Cambrian  and  recent 128 

26.  Chaetognaths,  Cambrian  and  recent 129 

27.  Jellyfish,  Cambrian  and  recent 130 

28.  The  twelve  chief  habitat  zones ^31 

29.  Life  zones  of  Cambrian  and  recent  invertebrates 131 

30.  Map — North  America  in  Cambrian  times 132 

31.  Sea-scorpions  of  Silurian  times ^33 

32.  Map — North  America  in  Middle  Devonian  times i34 

33.  Changing  environment  during  fifty  million  years i35 

34.  Fossil  starfishes ^3° 

35.  Mutations  of  Waagen  in  ammonites ^39 

36.  Mutations  of  Spirijer  mucronatus i40 

37.  Shell  pattern  and  tooth  pattern  of  Glyptodon 148 

38.  Teeth  of  Euprotogonia  and  Meniscotherium i49 

39.  Adaptation  of  the  fingers  in  a  lemur 150 

40.  Total  geologic  time  scale ^53 

41.  Adaptation  of  form  in  three  marine  vertebrates— shark,  ichthyosaur, 

and  dolphin ^55 

42.  Chronologic  chart  of  vertebrate  succession 161 

43.  The  existing  lancelets  (Amphioxus) 162 

44.  Five  types  of  body  form  in  fishes 1^3 

45.  Mai>— North  America  in  Upper  Silurian  time 164 

46.  The  Ostracoderm  Palceaspis 165 

47.  The  Antiarchi.     Bothriolepis 1^5 

48.  The  Arthrodira.     Dinichthys  intcrmedius 166 

49.  A  primitive  Devonian  shark,  Cladoselache 167 

50.  Adaptive  radiation  of  the  fishes ^^^ 

51.  Fish  types  from  the  Old  Red  Sandstone 170 

52.  Map— the  world  in  Early  Lower  Devonian  times 171 

53.  Change  of  adaptation  in  the  limbs  of  vertebrates 172 


ILLUSTRATIONS  xxix 

"*'•  PAGE 

54.  Deep-sea  fishes — extremes  of  adaptation  in  locomotion  and  illumina- 

tion        jy^ 

55.  Phosphorescent  illuminating  organs  of  deep-sea  fishes 174 

56.  Map — North  America  in  Upper  Devonian  time 175 

57.  The  earliest  known  limbed  animal 176 

58.  A  primitive  amphibian j^y 

59.  Descent  of  the  Amphibia jyg 

60.  Chief  amphibian  types  of  the  Carboniferous 179 

61.  Skull  and  vertebral  column  of  Z)x/>/ocaw/Ms 180 

62.  Map — the  world  in  Earliest  Permian  time 181 

63.  Amphibia  of  the  American  Permo-Carboniferous 182 

64.  Skeleton  of  Eryops ig^ 

65.  Map — the  world  in  Earliest  Permian  time 185 

66.  Ancestral  reptilian  types 186 

67.  Reptiles  with  skulls  transitional  from  the  amphibian 187 

68.  Map — the  world  in  Middle  Permian  time 188 

69.  The  fin-back  Permian  reptiles 189 

70.  Mammal-like  reptiles  of  South  Africa 190 

71.  A  South  African  "dog-toothed"  reptile 192 

72.  Adaptive  radiation  of  the  Reptilia 193 

73-  Geologic  records  of  reptilian  evolution 195 

74.  Dinosaur  mummy— a  relic  of  flood-plain  conditions 197 

75-  Reptiles  leaving  a  terrestrial  for  an  aquatic  habitat 199 

76.  Convergent  adaptation  of  amphibians  and  reptiles 200 

77.  Adaptation  of  reptiles  to  the  aquatic  habitat  zones      .....  201 

78.  Alternating  adaptation  of  the  "leatherback"  turtles 202 

79.  The  existing ''leatherback"  turtle 202 

80.  Marine  adaptation  of  terrestrial  Chelonia 203 

81.  Marine  pelagic  adaptation  of  the  ichthyosaurs 204 

82.  Restorations  of  two  ichthyosaurs 205 


l) 


XXX  ILLUSTRATIONS 

PAGE 
TIG.  .  ^ 

SS.  Map— North  America  in  Upper  Cretaceous  time ^^ 

84.  Convergent  forms  of  aquatic  reptiles ^07 

85.  A  plesiosaur  from  the  Jurassic  of  England 207 

86.  Types  of  marine  pelagic  plesiosaurs 

87.  Tylosaurus,  a  sea  lizard 

88.  Upper  Triassic  life  of  the  Connecticut  River 211 

89.  Terrestrial  evolution  of  the  dinosaurs ^ii 

90.  Map— North  America  in  Upper  Triassic  time 212 

91.  A  carnivorous  dinosaur  preying  upon  a  sauropod 213 

92.  Extreme  adaptation  in  the 'Hyrant"  and  "ostrich  "dinosaurs     .      .  214 

93.  Four  restorations  of  the ''ostrich"  dinosaur 215 

94.  Anchisanrus  and  Plateosaurus  compared 21 

95.  Map— the  world  in  Lower  Cretaceous  time 217 

96.  Map— North  America  in  Lower  Cretaceous  time 218 

97.  Three  principal  types  of  sauropods ^^^ 

98.  Terrestrio-fluviatile  theory  of  the  habits  of  .l/>a/05a«rw5    ....     220 

99.  Primitive  iguanodont  Camptosaiiriis 

100.  Upper  Cretaceous  iguanodonts  from  Montana 222 

loi.     Adaptive  radiation  of  the  iguanodont  dinosaurs 223 

102.  Tyrannosaurus   and    Ceratopsia-offensive   and   defensive   energy     ^^^ 

complexes 

103.  Restoration  of  the  Pterodactyl 

2  2  7 

104.  Ancestral  tree  of  the  birds 

105.  Skeletons  of  ^rcZ/^^/'/^O'^  and  pigeon  compared 228 

106.  Silhouettes  of  ArchcEOpteryx  and  pheasant 

107.  Four  evolutionary  stages  in  the  four-winged  bird 228 

108.  Parachute  flight  of  the  primitive  bird 229 

109.  Restoration  of  Archceopteryx 

no.     Reversed  aquatic  evolution  of  wing  and  body  form 230 

III.     The  sei  whale,  BalcBHOptera  hor calls ^34 


ILLUSTRATIONS  xxxi 

FIG.  PAGE 

112.  The  tree  shrew,  Tupaia 235 

113.  Primitive  types  of  monotreme  and  marsupial 235 

114.  Ancestral  tree  of  the  mammals 236 

115.  Adaptive  radiation  of  the  mammals 239 

116.  Alternating  adaptation  in  the  kangaroo  marsupials 243 

117.  Evolution  of  proportion.     Okapi  and  giraffe 248 

118.  Brachydactyly  and  dolichodactyly 249 

119.  Result  of  removing  the  thyroid  and  parathyroid  glands  .      .      .      .  250 

120.  Result  of  removing  the  pituitary  body 251 

121.  Main  subdivisions  of  geologic  time 256 

122.  Map — North  Polar  theory  of  the  distribution  of  mammals  .      .      .  257 

123.  Scene  in  western  Wyoming  in  Middle  Eocene  times 258 

124.  Two  stages  in  the  early  evolution  of  the  ungulates 259 

125.  A  primitive  whale  from  the  Eocene  of  Alabama 260 

126.  Map — North  America  in  Upper  Oligocene  time 262 

127.  Two  stages  in  the  evolution  of  the  titanotheres 263 

128.  Evolution  of  the  horn  in  the  titanotheres 264 

129.  Horses  of  Oligocene  time 266 

130.  Stages  in  the  evolution  of  the  horse 267 

131.  Epitome  of  proportion  evolution  in  the  Proboscidea 269 

132.  Map — the  ice-fields  of  the  fourth  glaciation 270 

133.  Groups  of  reindeer  and  woolly  mammoth 271 

134.  Glacial  environment  of  the  woolly  rhinoceros 272 

135-  Pygmies  and  plainsmen  of  New  Guinea 273 

TABLES 

I.  Distribution  of  the  chemical  elements 33 

II.  Functions  of  the  life  elements to  face  67 


THE  ORIGIN  AND   EVOLUTION 

OF    LIFE 


I 


INTRODUCTION 

Four  questions  as  to  the  origin  of  life.  Vitalism  or  mechanism?  Creation 
or  evolution?  Law  or  chance?  The  energy  concept  of  hfe.  Newton  s 
laws  of  motion.  Action  and  reaction.  Imeraction.  The  four  complexes 
of  energy.     Darwin's  law  of  Natural  Selection. 

We  may  introduce  this  great  subject  by  putting  to  ourselves 
four  leading  questions:  First,  Is  life  upon  the  earth  something 
new?  Second,  Does  life  evolution  externally  resemble  stel- 
lar evolution  ?  Third,  Is  there  evidence  that  similar  internal 
physicochemical  laws  prevail  in  life  evolution  and  in  lifeless 
evolution?  Fourth,  Are  life  forms  the  result  of  law  or  of 
chance  ? 

FoiiR  Questions  as  to  the  Origin  or  Life 

Our  first  question  is  one  which  has  not  yet  been  answered 
by  science,'  although  there  are  two  opinions  regarding  it.  Does 
the  origin  of  life  represent  the  beginning  of  something  new  in 
the  cosmos,  or  does  it  represent  the  continuation  and  evolu- 
tion of  forms  of  matter  and  energy  already  found  in  the  earth, 
in  the  sun,  and  in  the  other  stars  ? 

The  traditional  opinion  is  that  something  new  entered  this  \ 
and  possibly  other  planets  with  the  appearance  of  life;  this 
view  is  also  involved  in  all  the  older  and  newer  hypotheses 

•  Science  consists  of  the  body  of  well-ascertained  and  verified  facts  and  laws  of  nature 
It  is  clearly  to  K  distinguished  from  the  mass  of  theories,  hypotheses,  and  opmions  which 
are  of  value  in  the  progress  of  science. 


2  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

which  group  around  the  idea  of  vitalism  or  the  existence  of 
specific,  distinctive,  and  adaptive  energies  in  Hving  matter- 
energies  which  do  not  occur  in  Ufeless  matter. 

The  more  modern  scientific  opinion  is  that  Hfe  arose  from 
a  recombination  of  forces  pre-existing  in  the  cosmos.  To  hold 
to  this  opinion,  that  Hfe  does  not  represent  the  entrance  either 
of  a  new  form  of  energy  or  of  a  new  series  of  laws,  but  is  sim- 
ply another  step  in  the  general  evolutionary  process,  is  cer- 
tainly consistent  with  the  development  of  mechanics,  physics, 
and  chemistry  since  the  time  of  Newton  and  of  evolutionary 
thought  since  Buflon,  Lamarck,  and  Darwin.  Descartes  (1644) 
led  all  the  modern  natural  philosophers  in  perceiving  that  the 
explanation  of  life  should  be  sought  in  the  physical  terms  of 
motion  and  matter.  Kant  at  first  (i75S-i77S)  adopted  and 
later  (1790)  receded  from  this  opinion. 

These  contrasting  opinions,  which  are  certainly  as  old  as 
Greek  philosophy  and  probably  much  older,  are  respectively 
known  as  the  vitalistic  and  the  mechanistic. 

We  may  express  as  our  own  opinion,  based  upon  the  appli- 
cation of  uniformitarian  evolutionary  principles,  that  when 
life  appeared  on  the  earth  some  energies  pre-existing  in  the 
cosmos  were  brought  into  relation  with  the  chemical  elements 
already  existing.  In  other  words,  since  every  advance  thus 
far  in  the  quest  as  to  the  nature  of  life  has  been  in  the  direc- 
tion of  a  physicochemical  rather  than  of  a  vitalistic  explanation, 
from  the  time  when  Lavoisier  (i 743-1 794)  put  the  life  of  plants 
on  a  solar-chemical  basis,  if  we  logically  follow  the  same  direc- 
tion we  arrive  at  the  belief  that  the  last  step  into  the  unknown 
—one  which  possibly  may  never  be  taken  by  man— will  also  be 
physicochemical  in  all  its  measurable  and  observable  proper- 
ties, and  that  the  origin  of  life,  as  well  as  its  development,  will 
ultimately  prove  to  be  a  true  evolution  within  the  pre-existing 


i 


FOUR  QUESTIONS  REGARDING  LIFE  3 

cosmos.  Without  being  either  a  mechanist  or  a  materialist,  one 
may  hold  the  opinion  that  life  is  a  continuation  of  the  evolu- 
tionary process  rather  than  an  exception  to  the  rest  of  the 
cosmos,  because  both  mechanism  and  materialism  are  words 
borrowed  from  other  sources  which  do  not  in  the  least  con- 
vey the  impression  which  the  activities  of  the  cosmos  make 
upon  us.  This  impression  is  that  of  limitless  and  ordered 
energy. 

Our  second  great  question  relates  to  the  exact  significance 
of  the  term  evolution  when  applied  to  Ufeless  and  to  Hving 
matter.  Is  the  development  of  life  evolutionary  in  the  same 
sense  or  is  it  essentially  different  from  that  of  the  inorganic 
world?  Let  us  critically  examine  this  question  by  comparing 
the  evolution  of  life  with  what  is  known  of  the  evolution  of 
the  stars,  of  the  formation  of  the  earth;  in  brief,  of  the  com- 
parative anatomy  and  physiology  of  the  universe  as  developed 
by  the  physicist  Rutherford,^  by  the  astronomer  CampbeU,^ 
and  by  the  geologist  Chamberlin.'^  Or  we  may  compare  the 
evolution  of  Hfe  to  the  possible  evolution  of  the  chemical  ele- 
ments themselves  from  simpler  forms,  in  passing  from  primitive 
nebulie  through  the  hotter  stars  to  the  planets,  as  first  pointed 
out  by  Clarke^  in  1873,  and  by  Lockyer  in  1874. 

In  such  comparisons  do  we  find  a  correspondence  between 
the  orderly  development  of  the  stars  and  the  orderly  develop- 
ment of  Hfe  ?  Do  we  observe  in  life  a  continuation  of  processes 
which  in  general  present  a  picture  of  the  universe  slowly  cool- 
ing off  and  running  down?  Or,  after  hundreds  of  milHons  of 
years  of  more  or  less  monotonous  repetition  of  purely  physico- 
chemical  and  mechanical  reaction,  do  we  find  that  electrons, 


*  Rutherford,  Sir  Ernest,  191 5. 

»  Chamberlin,  Thomas  Chrowder,  19 16. 


2  Campbell,  William  Wallace,  191 5. 
<  Clarke,  F.  W.,  1873,  P-  323- 


4  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

atoms,  and  molecules  break  forth  into  new  forms  and  mani- 
festations of  energy  which  appear  to  be  ^^ creative/'  convey- 
ing to  our  eyes  at  least  the  impression  of  incessant  genesis  of 
new  combinations  of  energy,  of  matter,  of  form,  of  function, 

of  character? 

To  our  senses  it  appears  as  if  the  latter  view  were  the  cor- 
rect one,  as  if  something  new  is  breathed  into  the  aging  dust, 
as  if  the  first  appearance  of  life  on  this  planet  marks  an  actual 
reversal  of  the  previous  order  of  things.     Certainly  the  cosmic 
processes  cease  to  run  down  and  begin  to  build  up,  abandoning 
old  forms  and  constructing  new  ones.     Through  these  activities 
within  matter  in  the  Uving  state  the  dying  earth,  itself  a  mere 
cinder  from  the  sun,  develops  new  chemical  compounds;    the 
chemical  elements  of  the  ocean  are  enriched  from  new  sources 
of  supply,  as  additional  amounts  of  chemical  compounds,  pro- 
duced by  organisms  from  the  soil  or  by  elements  in  the  earth 
that  were  not  previously  dissolved,  are  liberated  by  life  proc- 
esses and  ultimately  carried  out  to  sea;    the  very  composition 
of  the  rocks  is  changed;    a  new  life  crust  begins  to  cover  the 
earth  and  to  spread  over  the  bottom  of  the  sea.     Our  old  in- 
organic planet  is  reorganized,  and  we  see  in  living  matter  a 
reversal  of  the  melancholy  conclusion  reached  by  CampbelP 
that  ^^  Everything  in  nature  is  growing  older  and  changing  in 
condition;     slowly  or  rapidly,  depending  upon  circumstances; 
the  meteorological  elements  and  gravitation  are  tearing  down 
the  high  places  of  the  earth;    the  eroded  materials  are  trans- 
ported to  the  bottoms  of  valleys,  lakes,  and  seas;    and  these 
results  beget  further  consequences.'' 

Thus  it  certainly  appears,  in  answer  to  our  second  ques- 
tion, that  living  matter  does  not  follow  the  old  evolutionary  or- 
der, but  represents  a  new  assemblage  of  energies  and  new  types 

1  Campbell,  William  Wallace,  1915,  P-  209. 


\    ( 


FOUR  QUESTIONS  REGARDING  LIFE  5 

of  action,  reaction,  and  interaction— to  use  the  terms  of  ther- 
modynamics—between those  chemical  elements  which  may  be 
as  old  as  the  cosmos  itself,  unless  they  prove  to  represent  an 
evolution  from  still  simpler  elements. 

Such  evolution,  we  repeat  with  emphasis,  is  not  like  that 
of  the  chemical  elements  or  of  the  stars;  the  evolutionary  proc- 
ess now  takes  an  entirely  new  and  different  direction.  Al- 
though it  may  arise  through  combinations  of  pre-existing  ener- 
gies, it  is  essentially  constructive  and  apparently  though  not 
actually  creative;^  it  is  continually  giving  birth  to  an  infinite 
variety  of  new  forms  and  functions  which  never  appeared  in 
the  universe  before.  It  is  a  continuous  creation  or  creative 
evolution.  Although  this  creative  power  is  something  new 
derived  from  the  old,  it  presents  the  first  of  the  numerous  con- 
trasts between  the  living  and  the  lifeless  world. 

Our  third  great  question,  however,  relates  to  the  continua- 
tion of  the  same  physicochemical  laws  in  living  as  in  Hfeless 
matter,  and  puts  the  second  question  in  another  aspect.  Is 
there  a  creation  in  the  strict  sense  of  the  term,  namely,  that 
some  new  form  of  energy  arises?  No,  so  far  as  we  observe, 
the  process  is  still  evolutionary  rather  than  creative,  because  all 
the  new  characters  and  forms  of  life  appear  to  arise  out  of  new 
combinations  of  pre-existing  matter.  In  other  words,  the  old 
forms  of  energy  transformations  appear  to  be  taking  a  new 

direction. 

I  shall  attempt  to  show  that  since  in  their  simple  forms 
living  processes  are    known  to  be  physicochemical    and  are 

^Creation  (L.  crealio,  creare,  pp.  creatus;  akin  to  Gr.  Kpaiv^uv,  complete;  Sanskrit, 
Wkar,  make),  in  contradistinction  to  evolution,  is  the  production  of  somethmg  new  out 
of  nothing,  the  act  of  producing  both  the  material  and  the  form  of  that  which  is  made. 
Evolution  is  the  production  of  something  new  out  of  the  building-up  and  recombination 
of  something  which  already  exists. 


6  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

more  or  less  clearly  interpretable  in  terms  of  action,  reaction, 
and  interaction,  we  are  compelled  to  believe  that  complex,  forms 
will  also  prove  to  be  interpretable  in  the  same  terms.  None 
the  less,  if  we  affirm  that  the  entire  trend  of  our  observation 
is  in  the  direction  of  physicochemical  explanations  rather  than 
of  vitahsm  and  vitalistic  hypotheses,  this  is  very  far  from 
affirming  that  the  explanation  of  life  is  purely  materialistic, 
or  purely  mechanistic,  or  that  any  of  the  present  physico- 
chemical  explanations  are  final  or  satisfying  to  our  reason. 

Chemists  and  biological  chemists  have  very  much  more  to 
discover.  May  there  not  be  in  the  assemblage  of  cosmic  chem- 
ical elements  necessary  to  life,  which  we  shall  distinguish  as 
the  ''life  elements,''  some  known  element  which  thus  far  has 
not  betrayed  itself  in  chemical  analysis  ?  This  is  not  impossi- 
ble, because  a  known  element  like  radium,  for  example,  might 
well  be  wrapped  up  in  living  matter  but  remain  as  yet  unde- 
tected, owing  to  its  suffusion  or  presence  in  excessively  small 
quantities  or  to  its  possession  of  properties  that  have  escaped 
notice.  Or,  again,  some  unknown  chemical  element,  to  which 
the  hypothetical  term  hion  might  be  given,  may  lie  awaiting 
discovery  within  this  complex  of  known  elements.  Or  an 
unknown  source  of  energy  may  be  active  here. 

It  is,  however,  far  more  probable  from  our  present  state  of 
knowledge  that  unknown  principles  of  action,  reaction,  and 
interaction  between  living  forms  await  discovery;  such  prin- 
ciples are  indeed  adumbrated  in  the  as  yet  partially  explored 
activities  of  various  chemical  messengers  in  the  bodies  of 
j)lants  and  animals. 

We  are  now  prepared  for  the  fourth  of  our  leading  questions. 
If  it  be  determined  that  the  evolution  of  non-living  matter 
follows  certain  physical  laws,  and  that  the  living  world  con- 


.  i 


FOUR  QUESTIONS  REGARDING  LIFE  ^ 

forms  to  many  if  not  to  all  of  these  laws,  the  final  question 
which  arises  is:  Does  the  living  world  also  conform  to  law  in 
its  most  important  aspect,  namely,  that  of  fitness  or  adapta- 
tion, or  does  law  emerge  from  chance?  In  other  words,  in 
the  origin  and  evolution  of  living  things,  does  nature  make  a 
departure  from  its  previous  orderly  procedure  and  substitute 
chance  for  law?  This  is  perhaps  the  very  oldest  biologic 
question  that  has  entered  the  human  mind,  and  it  is  one  on 
which  the  widest  difference  of  opinion  exists  even  to-day. 

Let  us  first  make  clear  what  we  mean  by  the  distinction 
between  law  and  chance. 

Astronomers  have  described  the  orderly  development  of 
the  stars,  and  geologists  the  orderly  development  of  the  earth: 
is  there  also  an  orderly  development  of  fife?  Are  Ufe  forms, 
like  celestial  forms,  the  result  of  law  or  are  they  the  result  of 

chance  ? 

That  life  forms  have  reached  their  present  stage  through 
the  operations  of  chance  has  been  the  opinion  held  by  a  great 
fine  of  natural  philosophers  from  Democritus  and  Empedocles 
to  Darwin,  and  including  Poulton,  de  Vries,  Bateson,  Morgan, 
Loeb,  and  many  others  of  our  own  day. 

Chance  is  the  very  essence  of  the  original  Darwinian  selec- 
tion hypothesis  of  evolution.  William  James^  and  many  other 
eminent  philosophers  have  adopted  the  '^chance''  view  as  if/ 
it  had  been  actually  demonstrated.  Thus  James  observes: 
'*  Absolutely  impersonal  reasons  would  be  in  duty  bound  to 
show  more  general  convincingness.  Causation  is  indeed  too  • 
obscure  a  principle  to  bear  the  weight  of  the  whole  structure 
of  theology.  As  for  the  argument  from  design,  see  how  Dar- 
winian ideas  have  revolutionized  it.  Conceived  as  we  now 
conceive  them,  as  so  many  fortunate  escapes  from  almost  lim- 

1  James,  William,  1902,  pp.  437-439- 


4 

■I 


8 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


itless  processes  of  destruction,  the  benevolent  adaptations 
which  we  find  in  nature  suggest  a  deity  very  different  from  the 
one  who  figured  in  the  earUer  versions  of  the  argument.  The 
fact  is  that  these  arguments  do  but  follow  the  combined  sug- 
gestions of  the  facts  and  of  our  feeling.  They  prove  nothing 
rigorously.  They  only  corroborate  our  pre-existent  partiali- 
ties." Again,  to  quote  the  opinion  of  a  recent  biological  writer: 
''And  why  not?  Nature  has  always  preferred  to  work  by  the 
hit-or-miss  methods  of  chance.  In  biological  evolution  mil- 
lions of  variations  have  been  produced  that  one  useful  one 

might  occur."  ^ 

I  have  long  maintained  that  this  opinion  is  a  biological 
dogma; 2  it  is  one  of  the  string  of  h>T>o theses  upon  which  Dar- 
win hung  his  theory  of  the  origin  of  adaptations  and  of  species, 
a  hypothesis  which  has  gained  credence  through  constant  re- 
iteration, for.  I  do  not  know  that  it  has  ever  been  demon- 
strated through  the  actual  observation  of  any  evolutionary 

series. 

That  life  forms  have  arisen  through  law  has  been  the  opinion 
of  another  school  of  natural  philosophers,  headed  by  Aristotle, 

^the  opponent  of  Democritus  and  Empedocles.  This  opinion 
has  fewer  scientific  and  philosophical  adherents i'^yet  Eucken,^ 
following  Schopenhauer,  has  recently  expressed  it  as  follows: 

/''From  the  very  beginning  the  predominant  philosophical  ten- 
dency has  been  against  the  idea  that  all  the  forms  we  see  around 
us  have  come  into  existence  solely  through  an  accumulation  of 
accidental  individual  variations,  by  the  mere  blind  concurrence 
of  these  variations  and  their  actual  survival,  without  the  op- 


1  Davies,  G.  R.,  1916,  p.  583.  ^      ^       ^  u  •    j-    •  1  a  uv  a  ^  \ 

2  Biology,  like  theology,  has  its  dogmas.  Leaders  have  their  disciples  and  blind  fol- 
lowers. All' great  truths,  like  Darwin's  law  of  selection,  acquire  a  momentum  which 
sustains  half-truths  and  pure  dogmas. 

3Eucken,  Rudolf,  1912,  p.  257. 


FOUR  QUESTIONS  REGARDING  LIFE  9 

eration  of  any  inner  law.     Natural  science,  too,  has  more  and 
more  demonstrated  its  inadequacy/' 

A  modern  chemist  also  questions  the  probability  of  the  en- 
vironmental fitness  of  the  earth  for  life  being  a  mere  chance 
process,  for  Hejnderson  remarks:    ^^ There  is,  in  truth,  not  one  ^ 
chance  'in  countless  millions  of  millions  that  the  many  unique 
properties  of  carbon,  hydrogen,  and  oxygen,  and  especially  of 
their  stable  compounds,  water  and  carbonic  acid,  which  chiefly 
make  up  the  atmosphere  of  a  new  planet,  should  simultaneously 
occur  in  the  three  elements  otherwise  than  through  the  opera- 
tion of  a  natural  law  which  somehow  connects  them  together. 
There  is  no  greater  probability  that  these  unique  properties 
should  be  without  due  cause  uniquely  favorable  to  the  organic 
mechanism.     These  are  no  mere  accidents;   an  explanation  is 
to  seek.     It  must  be  admitted,  however,  that  no  explanation 

is  at  hand."^ 

Unlike  our  first  question  as  to  whether  the  principle  of  life 
introduced  something  new  in  the  cosmos,  a  question  which  is 
still  in  the  stage  of  pure  speculation,  this  fourth  question  of 
law  versus  chance  in  the  evolution  of  Hfe  is  no  longer  a  matter 
of  opinion,  but  of  direct  observation.     So  far  as  law  is  con- 
cerned, we  observe  that  the  evolution  of  life  forms  is  hke  that 
of  the' stars:  their  origin  and  evolution  as  revealed  through 
paleontology  go  to  prove  that  Aristotle  was  essentially  right 
when  he  said  that  ^'Nature  produces  those  things  which,  being 
continually  moved  by  a  certain  principle  contained  in  them- 
selves, arrive  at  a  certain  end."^     What  this  internal  moving 
principle  is  remains  to  be  discovered.     We  may  first  exclude 
the  possibility  that  it  acts  either  through  supernatural  or  teleo- 
logic  interposition  through  an  externally  creative  power.     Al- 
though its  visible  results  are  in  a  high  degree  purposeful,  we 

^  Henderson,  Lawrence  J.,  1913,  P-  2/6.  '  Osborn,  H.  F.,  1894,  p.  56. 


lO 


THE  ORIGIN  AND   EVOLUTION  OF   LIFE 


may  also  exclude  as  unscientific  the  vitalistic  theory  of  an 
entelechy  or  any  other  form  of  internal  perfecting  agency  dis- 
tinct from  known  or  unknown  physicochemical  energies. 

Since  certain  forms  of  adaptation  which  were  formerly 
mysterious  can  now  be  explained  without  the  assumption  of 
an  entelechy  we  are  encouraged  to  hope  that  all  forms  may 
be  thus  explained.  The  fact  that  the  causes  underlying  the 
origin  of  many  forms  of  adaptation  are  still  unknown,  uncon- 
ceived,  and  perhaps  inconceivable,  does  not  inhibit  our  opinion 
that  adaptation  will  prove  to  be  a  continuation  of  the  previous 
cosmic  order  rather  than  the  introduction  of  a  new  order  of 
things.  If,  however,  we  reject  the  vitalistic  hypotheses  of  the 
ancient  Greeks,  and  the  modern  vitalism  of  Driesch,  of  Bergson, 
and  of  others,  we  are  driven  back  to  the  necessity  of  further 
experiment,  observation,  and  research,  guided  by  the  imagina- 
tion and  checked  by  verification.  As  indicated  in  our  Pref- 
ace, the  old  paths  of  research  have  led  nowhere,  and  the 
question  arises:  What  lines  shall  new  researches  and  experi- 
ments follow? 


The  Energy  Concept  of  Life 


While  we  owe  to  matter  and  form  the  revelation  of  the 
existence  of  the  great  law  of  evolution,  we  must  reverse  our 
thought  in  the  search  for  causes  and  take  steps  toward  an 
energy  conception  of  the  origin  of  life  and  an  energy  conception 
of  the  nature  of  heredity. 

So  far  as  the  creative  power  of  energy  is  concerned,  we 
are  on  sure  ground:  in  physics  energy  controls  matter  and 
form;  in  physiology  function  controls  the  organ;  in  animal 
mechanics  motion  controls  and,  in  a  sense,  creates  the  form  of 
muscles  and  bones.     In  every  instance  some  kind  of  energy 


THE  ENERGY  CONCEPT  OF  LIFE 


II 


or  work  precedes  some  kind  of  form,  rendering  it  probable 
that  energy  also  precedes  and  controls  the  evolution  of  life. 

The  total  disparity  between  invisible  energy  and  visible 
form  is  the  second  point  which  strikes  us  as  in  favor  of  such 
a  conception,  because  the  most  phenomenal  thing  about  the 
heredity-germ  is  its  microscopic  size  as  contrasted  with  the 
titanic  beings  which  may  rise  out  of  it.     The  electric  energy 
transmitted  through  a  small  copper  wire  is  yet  capable  of  mov- 
ing a  long  and  heavy  train  of  cars.     The  discovery  by  Bec- 
querel  and  Curie  of  radiant  energy  and  of  the  properties  of 
radium  helps  us  in  the  same  way  to  understand  an  energy 
conception  of    the   heredity-germ,  for  in   radium  the   energy 
per  unit  of  mass  is  enormously  greater  than  the  energy  quanta 
which  we  were  accustomed  to  associate  with  units  of  mass; 
whereas,   in  most  man-made  machines  with  metallic  wheels 
and  levers,  and  in  certain  parts  of  the  animal  machine  con- 
structed of  muscle  and  bone,  the  work  done  is  proportionate 
to  the  size  and  form.     The  slow  dissipation  or  degradation  of 
energy  in  radium  has  been  shown  by  Curie  to  be  concomitant 
with  the  giving  off  of  an  enormous  amount  of  heat,  while 
Rutherford  and  Strutt  declare  that  in  a  very  minute  amount 
of  active  radium   the  energy  of  degradation  would  entirely 
dominate  and  mask  all  other  cosmic  modes  of  transformation 
of  energy;   for  example,  it  far  outweighs  that  arising  from  the 
gravitational  energy  which  is  an  ample  supply  for  our  cosmic 
system,  the  explanation  being  that  the  minutest  energy  ele- 
ments of  which  radium  is  composed  are  moving  at  incredible 
velocities,  approaching  often  the  velocity  of  light,  f.  e.,  180,000 
miles  per   second.     The   energy   of   radium  differs  from   the 
supposed  energy  of  life  in  being  constantly  dissipated  and  de- 
graded; its  apparently  unlimited  power  is  being  lost  and  scat- 
tered. 


12 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


We  may  imagine  that  the  energy  which  lies  in  the  life-germ 
of  heredity  is  very  great  per  unit  of  mass  of  the  matter  which 
contains  it,  but  that  the  Hfe-germ  energy,  unlike  that  of  radium, 
is  in  process  of  accumulation,  construction,  conservation,  rather 
than  of  dissipation  and  destruction. 

Following  the  time  (1620)  when  Francis  Bacon  divined  that 
heat  consists  of  a  kind  of  motion  or  brisk  agitation  of  the  par- 
ticles of  matter,  it  has  step  by  step  been  demonstrated  that 
the  energy  of  heat,  of  light,  of  electricity,  the  electric  energy 
of  chemical  configurations,  the  energy  of  gravitation,  are  all 
utilized  in  Uving  as  well  as  in  Ufeless  substances.  Moreover, 
as  remarked  above  (p.  5),  no  form  of  energy  has  thus  far 
been  discovered  in  Hving  substances  which  is  peculiar  to  them 
and  not  derived  from  the  inorganic  world.  In  a  broad  sense 
all  these  manifestations  of  energy  are  subject  to  Newton's  dy- 
namical laws!  which  were  formulated  in  connection  with  the 
motions  of  the  heavenly  bodies,  but  are  found  to  apply  equaUy 
to  all  motions  great  or  Uttle. 

These  three  fundamental  laws  are  as  follows  i^ 


Corpus  omne  perseverare  in  statu 
suo  quiescendi  vel  movendi  uni- 
formiter  in  directum,  nisi  quatenus 
illud  a  viribus  impressis  cogitur 
statum  suum  mutare. 


Every  body  perseveres  in  its 
state  of  rest,  or  of  uniform  motion 
in  a  right  line,  unless  it  is  compelled 
to  change  that  state  by  forces  im- 
pressed thereon. 


^  I  am  indebted  to  my  colleague  M.I.  Pupin  for  valuable  suggestions  m  formuiatmg 
the  physical  aspect  of  the  principles  of  action  and  reaction.  He  mterprets  Newton's 
third  law  of  motion  as  the  foundation  not  only  of  modern  dynamics  m  the  Newtonian 
sense  but  in  the  most  general  sense,  including  biological  phenomena.  With  regard  to  the 
first  law  of  thermodynamics,  it  is  a  particular  form  of  the  principle  of  conservation  of  en- 
ergy as  applied  to  heat  energy;  Helmholtz,  who  first  stated  the  principle  of  conservation 
of  energy  derived  it  from  Newtonian  dynamics.  The  second  law  of  thermodynamics 
started  from  a  new  principle,  that  of  Carnot,  which  apparently  had  no  direct  connection 
with  Newton's  third  law  of  motion;  this  second  law,  however,  in  its  most  general  form 
cannot  be  fully  interpreted  except  by  statistical  dynamics,  which  are  a  modern  offshoot 

of  Newtonian  dynamics.  ,  .     ,,  ,    n  •     •.•    •      aq 

2  Newton's  three  laws  of  motion,  first  published  m  Newton  s  Pnncipia  in  1687. 


THE  ENERGY  CONCEPT  OF  LIFE 


13 


n 

Mu  tat  ion  em  motus  proportio- 
nalem  esse  vi  motrici  impressae,  et 
fieri  secundum  lineam  rectam  qua 
vis  ilia  imprimitur. 

Ill 

Actioni  contrariam  semper  et 
^qualem  esse  reactionem:  sive  cor- 
porum  duorum  actiones  in  se  mutuo 
semper  esse  aequales  et  in  partes 
contrarias  dirigi. 


II 


The  alteration  of  motion  is  ever 
proportional  to  the  motive  force 
impressed;  and  is  made  in  the  direc- 
tion of  the  right  line  in  which  that 
force  is  impressed. 

Ill 

To  every  action  there  is  always 
opposed  an  equal  reaction:  or  the 
mutual  actions  of  two  bodies  upon 
each  other  are  always  equal,  and 
directed  to  contrary  parts. 


Newton's  third  law  of  the  equality  of  action  and  reaction  is 
the  foundation  of  the  modern  doctrine  of  energy/  not  only  in 
the  Newtonian  sense  but  in  the  most  general  sense.^    Newton 
divined  the  principle  of  the  conservation  of  energy  m  mechanics; 
Rumford  (1798)  maintained  the  universality  of  _  the  laws  of 
energy;  Joule  (1843)  established  the  particular  principle  of  the 
conservation  of  energy,  namely  of  the  exact  equivalence  be- 
tween the  amount  of  heat  produced  and  the  amount  of  mechan- 
ical energy   destroyed;  and  Helmholtz  in  his  great  memoir 
dher  die  Erhaltung  der  Kraft  extended  this  system  of  conser- 
vation of  energy  throughout  the  whole  range  of  natural  phe- 
nomena.    A  familiar  instance  of  the  so-called  transformatton^  of 
energy  is  where  the  sudden  arrest  of  a  cool  but  rapidly  moving 
body  produces  heat.    This  was  developed  as  the  first  law  of 

thermodynamics. 

At  the  same  time  there  arose  the  distinction  between  po- 
tential energy,  which  is  stored  away  in  some  latent  form  or 
manner  so  that  it  can  be  drawn  upon  for  work-such  energy 

•The  term  Energy  (Gr.  Ivlpr-;   -  in;  IpTov,  -flZ''^J^:^e:tZc'i::^y''oi 
accumulated  capacity  for  doing  mechanical  work,  and  may  be  either  kmcHc  ^energy 
heat  or  motion)  or  potential  (latent  or  stored  energy). 
2  M.  I.  Pupin,  see  note  above. 


14 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


THE   ENERGY  CONCEPT  OF  LIFE 


15 


being  exemplified  mechanically  by  the  bent  spring,  chemi- 
cally by  gunpowder,  and  electrically  by  a  Leyden  jar — and 
kinetic  energy,  the  active  energy  of  motion  and  of  heat. 

While  all  active  mechanical  energy  or  work  may  be  con- 
verted into  an  equivalent  amount  of  heat,  the  opposite  process 
of  turning  heat  into  work  involves  more  or  less  loss,  dissipa- 
tion, or  degradation  of  energy.  This  is  known  as  the  second 
law  of  thermodynamics  and  is  the  outgrowth  of  a  principle  dis- 
covered by  Sadi  Carnot  (1824),  and  developed  by  Kelvin  (1852, 
1853).  The  far-reaching  conception  of  cyclic  processes  in  en- 
ergy enunciated  in  Kelvin's  principle  of  the  dissipation  of 
available  energy  puts  a  diminishing  limit  upon  the  amount  of 
heat  energy  available  for  mechanical  purposes.  The  available 
kinetic  energy  of  motion  and  of  heat  which  we  can  turn  into 
work  or  mechanical  effect  is  possessed  by  any  system  of  two 
or  more  bodies  in  virtue  of  the  relative  rates  of  motion  of  their 
parts,  velocity  being  essentially  relative. 

These  two  great  dynamical  principles  that  the  energy  of 
motion  can  be  converted  into  an  equivalent  amount  of  heat, 
and  that  a  certain  amount  of  heat  can  be  converted  into  a 
more  limited  amount  of  power  were  discovered  through  obser- 
vations on  the  motions  of  larger  masses  of  matter,  but  they 
are  believed  to  apply  equally  to  such  motions  as  are  involved 
in  the  smallest  electrically  charged  atoms  (ions)  of  the  chem- 
ical elements  and  the  particles  flying  off  in  radiant  energy  as 
phosphorescence.  Such  movements  of  infinitesimal  particles 
underlie  all  the  physicochemical  laws  of  action  and  reaction 
which  have  been  observed  to  occur  within  living  things.  In 
all  physicochemical  processes  within  and  without  the  organism 
by  which  energy  is  captured,  stored,  transformed,  or  released 
the  actions  and  reactions  are  equal,  as  expressed  in  Newton's 
third  law. 


4ii 


Actions  and  reactions  refer  chiefly  to  what  is  going  on  be- 
tween the  parts  of  the  organism  in  chemical  or  physical  con- 
tact, and  are  subject  to  the  two  dynamical  principles  referred 
to  above.     Interactions,  on  the  other  hand,  refer  to  what  is 
going  on  between  material  parts  which  are  connected  with 
each  other  by  other  parts,  and  cannot  be  analyzed  at  all  by  the 
two  great  dynamical  principles  alone  without  a  knowledge  of 
the  structure  which  connects  the  interacting  parts.     For  ex- 
ample, in  interaction  between  distant  bodies  the  cause  may  be 
very  feeble,  yet  the  potential  or  stored  energy  which  may  be 
liberated  at  a  distant  point  may  be  tremendous.     Action  and 
reaction  are  chiefly  simultaneous,  whereas  interaction  connects 
actions  and  reactions  which  are  not  simultaneous;  to  use  a 
simple  illustration:  when  one  pulls  at  the  reins  the  horse  feels 
it  a  little  later  than  the  moment  at  which  the  reins  are  pulled 
—there  is  interaction  between  the  hand  and  the  horse's  mouth, 
the   reins  being  the  interacting  part.     An  interacting  nerve- 
impulse  starting  from  a  microscopic  cell  in  the  brain  may  give 
rise  to  a  powerful  muscular  action  and  reaction  at  some  distant 
point.     An  interacting  enzyme,  hormone,  or  other  chemical 
messenger  circulating  in  the  blood  may  profoundly  modify  the 
growth  of  a  great  organism. 

Out  of  these  physicochemical  principles  has  arisen  the  con- 
ception of  a  living  organism  as  composed  of  an  incessant  series 
of  actions  and  reactions  operating  under  the  dynamical  laws 
which  govern  the  transfer  and  transformation  of  energy. 

The  central  theory  which  is  developed  in  our  speculation^ 
on  the  Origin  of  Life  is  that  every  physicochemical  action  and 
reaction  concerned  in  the  transformation,  conservation,  and 
dissipation  of  energy,  produces  also,  either  as  a  direct  result  or 
as  a  by-product,  a  physicochemical  agent  of  interaction  which 
permeates  and  affects  the  organism  as  a  whole  or  affects  only  some 


i6 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


special  part.  Through  such  interaction  the  organism  is  made 
a  unit  and  acts  as  one,  because  the  activities  of  all  its  parts 
are  correlated.  This  idea  may  be  expressed  in  the  follo\\ing 
simplified  scheme  of  the  functions  or  physiology  of  the  organism: 


ACTION     ] 

AND         |-  

REACTION  J 

Functions  of  the 

Capture,  Storage, 

and  Release  of 

Energy. 


INTERACTION 


-s-^  1 


Functions  of  the 

Coordination,  Balance, 

Cooperation,  Compensation, 

Acceleration,  Retardation, 

of  Actions  and  Reactions. 


ACTION 
AND 
[  REACTION 

Functions  of  the 

Capture,  Storage, 

and  Release  of 

Energy. 


Since  it  is  known  that  man\  actions  and  reactions  of  the 
organism — such  as  those  of  general  and  localized  growth,  of 
nutrition,  of  respiration — are  coordinated  with  other  actions 
and  reactions  through  interaction,  it  is  but  a  step  to  extend 
the  principle  and  suppose  that  all  actions  and  reactions  are  sim- 
ilarly coordinated;  and  that  while  there  was  an  evolution  of 
action  and  reaction  there  was  also  a  corresponding  evolution 
of  interaction,  for  without  this  the  organism  would  not  evolve 
harmoniously. 

Evidence  for  such  universality  of  the  interaction  principle 
has  been  accumulating  rapidly  of  late,  especially  in  experi- 
mental medicine^  and  in  experimental  biology.-  It  is  a  further 
/step  in  our  theory  to  suppose  that  the  directing  power  of  he' 
redity  which  regulates  the  initial  and  all  the  subsequent  steps 
of  development  in  action  and  reaction,  gives  the  orders,  hastens 
development  at  one  point,  retards  it  at  another,  is  an  elab- 
oration of  the  principle  of  interaction.     In  lowly  organisms 

1  See  the  works  of  Gushing  and  Crile  cited  below. 
*  See  the  recent  experiments  of  Morgan  and  Goodale. 


THE  ENERGY  CONCEPT  OF  LIFE 


17 


like  the  monads  these  interactions  are  very  simple;  in  higher 
organisms  like  man  these  interactions  are  elaborated  through 
physicochemical  and  other  agents,  some  of  which  have  already 
been  discovered  although  doubtless  many  more  await  discovery. 
Thus  we  conceive  of  the  origin  and  development  of  the  or- 
ganism as  a  concomitant  evolution  of  the  action,  reaction,  and 
interaction  of  energy.  Actions  and  reactions  are  borrowed 
from  the  inorganic  world,  and  elaborated  through  the  produc- 
tion of  the  new  organic  chemical  compounds ;  it  is  the  peculiar 
evolution  and  elaboration  of  the  physical  principle  of  inter- 
action which  distinguishes  the  living  organism. 

Thus  the  evolution  of  life  may  be  rewritten  in  terms  of  in- 
visible energy,  as  it  has  long  since  been  written  in  terms  of 
visible  form.  All  visible  tissues,  organs,  and  structures  are 
seen  to  be  the  more  or  less  simple  or  elaborate  agents  of  the 
different  modes  of  energy.  One  after  another  special  groups  of 
tissues  and  organs  are  created  and  coordinated— organs  for  the 
capture  of  energy  from  the  inorganic  environment  and  from  the 
life  environment,  organs  for  the  storage  of  energy,  organs  for 
the  transformation  of  energy  from  the  potential  state  into  the 
states  of  motion  and  heat.  Other  agents  of  control  are  evolved 
to  bring  about  a  harmonious  balance  between  the  various  or- 
gans and  tissues  in  which  energy  is  released,  hastened  or  ac- 
celerated,  slowed    down    or    retarded,   or    actually    arrested    or 

inhibited. 

In  the  simplest  organisms  energy  may  be  captured  while  the  V 
organism  as  a  whole  is  in  a  state  of  rest;  but  at  an  early  stage  of 
life  special  organs  of  locomotion  are  evolved  by  which  energy  is 
sought  out,  and  organs  of  prehension  by  which  it  may  be  seized. 
Along  with  these  motor  organs  are  developed  organs  of  offense 
and  defense  of  many  kinds,  by  means  of  which  stored  energy  is 


i8 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


protected  from  capture  or  invasion  by  other  organisms.  Finally, 
there  is  the  most  mysterious  and  comprehensive  process  of  all, 
by  which  all  these  manifold  modes  of  energy  are  reproduced  in 
(another  organism.  The  evolution  of  these  complex  modes  of 
action,  reaction,  and  interaction  is  traced  through  all  the  early 
chapters  of  this  volume  and  is  summed  up  in  Chapter  V  (p. 
152)  as  a  physicochemical  introduction  to  the  evolution  of  ver- 
tebrate form. 

The  Four  Complexes  of  Energy 

The  theoretic  evolution  of  the  four  complexes  is  somewhat 
as  follows: 

(i)  In  the  order  of  time  the  Inorganic  Environment  comes 
first;  energy  and  matter  are  first  seen  in  the  sun,  in  the  earth, 
in  the  air,  and  in  the  water — each  a  very  wonderful  complex 
of  energies  in  itself.  They  form,  nevertheless,  an  entirely 
orderly  system,  held  together  by  gravitation,  moving  under 
Newton's  law^s  of  motion,  subject  to  the  more  newly  discovered 
laws  of  thermodynamics.  In  this  complex  we  observe  actions 
and  reactions,  the  sum  of  the  taking  in  and  the  giving  out  of 
energy,  the  conservation  of  energy.  We  also  observe  inter- 
actions wherein  the  energy  released  at  certain  points  may  be 
greater  than  the  energy  received,  which  is  merely  a  stimulus  for 
the  beginning  of  the  local  energy  transformations.  This  energy 
is  distributed  among  the  eighty  or  more  chemical  elements  of 
the  sun  and  other  stars.  These  elements  are  combined  in  plants 
into  complex  substances,  generally  with  a  storage  of  energy. 
Such  substances  are  disintegrated  into  simple  substances  in  ani- 
mals, generally  with  a  release  of  energy.  All  these  processes 
are  termed  by  us  physicochemical. 


f 


h 


THE   FOUR  COMPLEXES  OF  ENERGY 


19 


(2)  With  life  something  new  appears  in  the  universe,^ 
namely,  a  union  of  the  internal  and  external  adjustment  of 
energy  which  we  appropriately  call  an  Organism,  In  the  course^ 
of  the  evolution  of  life  every  law  and  property  in  the  physico- 
chemical  world  is  turned  to  advantage;  every  chemical  ele- 
ment is  assembled  in  which  inorganic  properties  may  serve 
organic  functions.  There  is  an  immediate  or  gradual  separa- 
tion of  the  organism  into  two  complexes  of  energy,  namely, 
first,  the  energy  complex  of  the  organism,  which  is  perishable 
with  the  term  of  the  life  of  the  individual,  and  second,  the  germ 
or  heredity  substance,  which  is  perpetual. 

(3)  The  idea  that  the  germ  is  an  energy  complex  is  an  as 
yet  unproved  h>T>othesis;  it  has  not  been  demonstrated.  The 
Heredity-ger^n  in  some  respects  bears  a  likeness  to  latent  or 
potential  interacting  energy,  ^hile  in  other  respects  it  is  en- 
tirely unique.  The  supposed  germ  energy  is  not  only  cumula- 
tive but  is  in  a  sense  imperishable,  self -perpetuating,  and  con- 
tinuous during  the  whole  period  of  the  evolution  of  life  upon 
the  earth,  a  conception  which  we  owe  chiefly  to  the  law  of  the 
continuity  of  the  germ-plasm  formulated  by  Weismann.  Some 
of  the  observed  phenomena  of  the  germ  in  Heredity  are  chiefly 
analogous  to  those  of  interaction  in  the  Organism,  namely, 
directive  of  a  series  of  actions  and  reactions,/ but  in  general  we 
know  no  complete  physical  or  inorganic  analogy  to  the  phe- 
nomena of  heredity;  they  are  unique  in  nature. 

(4)  With  the  multiplication  and  diversification  of  individual 
organisms  there  enters  a  new  factor  in  the  environment,  namely, 
the  energy  complex  of  the  Life  Environment. 

Thus  there  are  combined  certainly  three,  and  possibly  four, 
complexes  of  energy,  of  which  each  has  its  own  actions,  reac- 
tions, and  interactions.     The  evolution  of  life  proceeds  by  sus- 


l 


20 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


taining  these  actions,  reactions,  and  interactions  and  con- 
stantly building  up  new  ones:  at  the  same  time  the  potentiaUty 
of  reproducing  these  actions,  reactions,  and  interactions  in  the 
course  of  the  development  of  each  new  organism  is  gradually 
being  accumulated  and  perpetuated  in  the  germ. 

From  the  very  beginning  every  individual  organism  is 
competing  with  other  organisms  of  its  own  kind  and  of  other 
kinds,  and  the  law  of  the  survival  of  the  fittest  is  operating 
between  the  forms  and  functions  of  organisms  as  a  whole  and 
between  their  separate  actions,  reactions,  and  interactions. 
This,  as  Weismann  pointed  out,  while  apparently  a  selection 
of  the  individual  organism  itself,  is  actually  a  selection  of  the 
heredity-germ  complex,  of  its  potentialities,  powers,  and  pre- 
dispositions. Thus  Selection  is  not  a  form  of  energy  nor  a  part 
of  the  energy  complex;  it  is  an  arbiter  between  different  com- 
plexes and  forms  of  energy;  it  antedates  the  origin  of  life  just 
as  adaptation  or  fitness  antedates  the  origin  of  life,  as  re- 
marked by  Henderson. 

Thus  we  arrive  at  a  conception  of  the  relations  of  organisms 
to  each  other  and  to  their  environment  as  of  an  enormous  and 
always  increasing  complexity,  sustained  through  the  interchange 
of  energy.  Darwin's  principle  of  the  survival  or  ehmination 
of  various  forms  of  Uving  energy  is,  in  fact,  adumbrated  in  the 
survival  or  elimination  of  various  forms  of  lifeless  energy  as 
witnessed  among  the  stars  and  planets.  In  other  words,  Dar- 
/win's  principle  operates  as  one  of  the  causes  of  evolution  in  mak- 
ing the  Ufeless  and  living  worlds  what  they  now  appear  to  be, 
but  not  as  one  of  the  energies  of  evolution.  Selection  merely 
determines  which  one  of  a  combination  of  energies  shall  survive 
\and  which  shall  perish. 

The  complex  of  four  interrelated  sets  of  physicochemical 
energies  which  I  have  previously  set  forth  (p.  xvi)  as  the  most 


THE  FOUR  COMPLEXES  OF  ENERGY 


21 


.. 


f 


fundamental  biologic  scheme  or  principle  of  development  may 
now  be  restated  as  follows: 

In  each  organism  the  phenomena  of  life  represent  the  action, 
reaction,  and  interaction  of  four  complexes  of  physicochemical 
energy,  namely,  those  of  (i)  the  Inorganic  Environment,  (2)  the 
developing  Organism  {protoplasm  and  body-chromatin),  (3)  the 
germ  or  Heredity-chromatin,  (4)  the  Life  Environment.  Upon 
the  resultant  actions,  reactions,  and  interactions  of  potential  and 
kinetic  energy  in  each  organism  Selection  is  constantly  operating 
wherever  there  is  competition  with  the  corresponding  actions,  re- 
actions, and  interactions  of  other  organisms} 

This  principle  I  shall  put  forth  in  different  aspects  as  the 
central  thought  of  these  lectures,  stating  at  the  outset  and 
often  recurring  to  the  admission  that  it  involves  several  unknown 
principles  and  especially  the  largely  hypothetical  question 
whether  there  is  a  relation  between  the  action,  reaction,  and 
interaction  of  the  internal  energies  of  the  germ  or  heredity- 
chromatin  with  the  external  energies  of  the  inorganic  environ- 
ment, of  the  developing  organism,  and  of  its  life  environment. 
In  other  words,  while  this  is  a  principle  which  largely  governs 
the  Organism,  it  remains  to  be  discovered  whether  it  also 
governs  the  causes  of  the  Evolution  of  the  Germ. 

As  observed  in  the  Preface  (p.  xvii)  we  are  studying  not  one 
but  four  simultaneous  evolutions.  Each  of  these  evolutions 
appears  to  be  almost  infinite  in  itself  as  soon  as  we  examine 
it  in  detail,  but  of  the  four  that  of  the  germ  or  heredity- 
chromatin  so  far  surpasses  all  the  others  in  complexity  that  it 
appears  to  us  infinite. 

The  physicochemical  relations  between  these  four  evolu- 
tions, including  the  activities  of  the  single  and  of  the  multiply- 
ing organisms  of  the  Life  Environment,  may  be  expressed  in 

1  Compare  Osborn,  H.  F.,  191 7,  P-  ^. 


< 


■i 
li 


22 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


diagrammatic  form,  and  somewhat  more  technically  than  in  the 
Preface,  as  follows: 


Organism  A 

Under 

Newton^ s  Laws  of  Motion 

and 
Modern  Thermodynamics 

Actions,  Reactions y  and 

Interactions 

of  the 

1.  Inorganic  Environment: 

physicochemical  en- 
ergies of  space,  of 
the  sun,  earth,  air, 
and  water. 

2.  Organism: 

physicochemical  en- 
ergies of  the  devel- 
oping individual  in 
the  tissues,  cells, 
protoplasm,  and 
cell-chromatin. 

3.  Heredity-Germ: 

physicochemical  en- 
ergies of  the  hered- 
ity-chromatin,  in- 
cluded in  the  re- 
productive cells 
and  tissues. 

4.  Life  Environment: 

I  physicochemical    en- 

ergies of  other  or- 
ganisms. 


Under 

Darwin  s  Law 

of 
Natural  Selection 

Survival  of  the 
fittest:  com- 
petition, selec- 
tion, and  elim- 
ination of  the 
energies  and 
forms. 


Organisms  B-Z 

Under 

Newton  s  Laws  of  Motion 

and 
Modern  Thermodynamics 

Actions,  Reactions,  and 

Interactions 

of  the 

1.  Inorganic  Environment: 

physicochemical  en- 
ergies of  space,  of 
the  sun,  earth,  air, 
and  water. 

2.  Organism: 

physicochemical  en- 
ergies of  the  devel- 
oping individual  in 
the  tissues,  cells, 
protoplasm,  and 
cell-chromatin. 

3.  Heredity-Germ: 

physicochemical  en- 
ergies of  the  hered- 
ity-chromatin  in- 
cluded in  the  re- 
productive cells 
and  tissues. 

4.  Life  Environment : 

physicochemical  en- 
ergies of  other  or- 
ganisms. 


/ 


THE   FOUR   COMPLEXES  OF  ENERGY 


2.3 


/ 


the  four  sets  of  internal  and  external  energies  which  play  upon 
and  within  every  individual  and  every  race.  In  respect  to 
form  it  is  ^^i^kaplasUc^  theory  in  the  sense  that  every  living 
plant  and  animal  form  is  plastically  moulded  by  four  sets  of 
energies.  The  derivation  of  this  conception  of  life  and  of  the 
possible  causes  of  evolution  from  the  laws  which  have  been 
developed  out  of  the  Newtonian  system,  and  from  those  of  the 
other  great  Cambridge  philosopher,  Charles  Darwin,  are  clearly 
shown  in  the  above  diagram. 

In  these  lectures  we  shall  consider  in  order,  first,  the  evo- 
lution of  the  inorganic  environment  necessary  to  life;  second, 
theories  of  the  origin  of  life  in  regard  to  the  time  w^hen  it  oc- 
curred and  the  accumulation  of  various  kinds  of  energy  through 
which  it  probably  originated;  and,  third,  the  orderly  develop- 
ment of  the  differentiation  and  adaptation  of  the  most  primi- 
tive forms.  Throughout  w^e  shall  point  out  some  of  the  more 
notable  examples  of  the  apparent  operation  of  our  fundamental 
biologic  principle  of  the  action,  reaction,  and  interaction  be- 
tween the  inorganic  environment,  the  organism,  the  germ,  and 
the  life  environment. 

The  apparently  insuperable  difficulties  of  the  problem  of 
the  causes  of  evolution  in  the  germ  or  heredity-chromatin — • 
causes  which  are  at  present  almost  entirely  beyond  the  realm 
of  observation  and  experiment — will  be  made  more  evident 
through  the  development  of  the  second  part  of  our  subject, 
namely,  the  evolution  of  the  higher  living  forms  of  energy 
upon  the  earth  so  far  as  they  have  been  followed  from  the 
stage  of  monads  or  bacteria  up  to  that  of  the  higher  mammals. 

^  Osborn,  H.  F.,  191 2.2. 


If  a  single  name  is  demanded  for  this  conception  of  evolu- 
tion it  might  be  termed  the  tetrakinetic  theory  in  reference  to 


PART  I.    THE  ADAPTATION  OF   ENERGY 

CHAPTER  I 
PREPARATION  OF  THE  EARTH  FOR  LIFE 

Primordial  environment— the  lifeless  earth.  Age  of  the  earth  and  beginning 
of  the  life  period.  Primordial  environment — the  lifeless  water.  Salt  as 
a  measure  of  the  age  of  the  ocean.  Primordial  chemical  environment. 
Primordial  environment — the  atmosphere. 

In  the  spirit  of  the  preparatory  work  of  the  great  pioneers 
of  geology,  such  as  Hutton,  Scrope,  and  Lyell,  and  of  the  his- 
tory of  the  evolution  of  the  working  mechanism  of  organic 
evolution,  as  developed  by  Darwin  and  Wallace,^  our  infer- 
ences as  to  past  processes  are  founded  upon  the  observation 
of  present  processes.  In  general,  our  narrative  will  therefore 
follow  the  ^'uniformitarian"  method  of  interpretation  first 
presented  in  1788  by  Hutton,-  who  may  be  termed  the  Newton 
of  geology,  and  elaborated  in  1830  by  Lyell,^  the  master  of 
Charles  Darwin.     The  uniformitarian  doctrine  is  this:  present 

/  continuity  implies  the  improbability  of  past  catastrophism  and 
violence  of  change,  either  in  the  lifeless  or  in  the  living  world; 
moreover,  we  seek  to  interpret  the  changes  and  laws  of  past 
time  through  those  which  we  observe  at  the  present  time. 

\  This  was  Darwin's  secret,  learned  from  Lyell. 

Cosmic  Primordial  Environment— The  Lifeless  Earth 

Let  us  first  look  at  the  cosmic  environment,  the  inorganic 
world  before  the  entrance  of  life.     Since  1825,  when  Cuvier^ 


1  Judd,  John  W.,  igio. 
=*  Lyell,  Charles,  1830. 


2  Hutton,  James,  1795. 

*  Cuvier,  Baron  Georges  L.  C.  F.  D.,  1825. 

24 


THE  LIFELESS  EARTH 


25 


^ 


published  his  famous  Discours  sur  les  Revolutions  de  la  Surface 
,Ju  Globe,  the  past  history  of  the  earth,  of  its  waters,  of  the 
atmosphere,  and  of  the  sun— the  four  great  complexes  of  in- 
organic environment— has  been  written  with  some  approach  to 
precision.  Astronomy,  physics,  chemistry,  geology,  and  pa- 
laeontology have  each  pursued  their  respective  lines  of  obser- 
vation, resulting  in  some  concordance  and  much  discordance 
of  opinion  and  theory.  In  general  we  shall  find  that  opinion 
founded  upon  life  data  has  not  agreed  with  opinion  founded 
upon  physical  or  chemical  data,  arousing  discord,  especially  in 
connection  with  the  problems  of  the  age  of  the  earth  and  the 
stabiUty  of  the  earth's  surface. 

In  our  review  of  these  matters  we  may  glance  at  opinions, 
whatever  their  source,  but  our  narrative  of  the  chemical  origin 
and  history  of  life  on  the  earth  will  be  followed  by  observations 
on  living  matter  mainly  as  it  is  revealed  in  palaeontology  and 
as  it  exists  to-day,  rather  than  on  hypotheses  and  speculations 
upon  pre-existing  states. 

The  formation  of  the  earth's  surface  is  a  prelude  to  our 
considering  the  first  stage  of  the  environment  of  Kfe.  Accord-^ 
ing  to  the  planetesimal  theory,  as  set  forth  by  Chambernn,^  the 
earth,  instead  of  consisting  of  a  primitive  molten  globe  as  pos- 
tulated by  the  old  nebular  hypothesis  of  Laplace,  originated  in 
a  nebulous  knot  of  soHd  matter  as  a  nucleus  of  growth  which 
was  fed  by  the  infall  or  accretion  of  scattered  nebulous  matter 
(planetesimals)  coming  within  the  sphere  of  control  of  this 
knot.  The  temperature  of  these  accretions  to  the  early  earth 
could  scarcely  have  been  high,  and  the  mode  of  addition  of 
these  planetesimals  one  by  one  explains  the  very  heterogeneous 
matter  and  differentiated  specific  gravity  of  the  continents  and 
oceanic  basins.     The  present  form  of  the  earth's  surface  is  the 

>  Chamberiin,  Thomas  Chrowder,  1916. 


26 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


result  of  the  combined  action  of  the  Hthosphere  (the  rocks), 
hydrosphere  (the  water),  and  atmosphere  (the  air).     Liquefac- 
tion of  the  rocks  occurred  locally  and  occasionally  as  the  result 
of  heat  generated  by  increased  pressure  and  by  radioactivity; 
but    the   planetesimal   hypothesis   assumes    that    the   present 
elastic  rigid  condition  of  the  earth  prevailed— at  least  in  its 
outer  half— throughout  the  history  of  its  growth  from  the  small 
original  nebular  knot  to  its  present  proportions  and  caused  the 
permanence  of  its  continents  and  of  its  oceanic  basins.     We 
are  thus  brought  to  conditions  that  are  fundamental  to  the 
\  evolution  of  life  on  the  earth.     According  to  the  opinion  of 
Chamberlin,  cited  by  Pirsson  and  Schuchert,^  life  on  the  earth 
may  have  been  possible  when  it  attained  the  present  size  of 

Mars. 

According  to  Becker,-  who  follows  the  traditional  theory  of 
a  primitive  molten  globe,  the  earth  first  presented  a  nearly 
smooth,  equipotential  surface,  determined  not  by  its  mineral 
composition,  but  by  its  density.     As  the  surface  cooled  down 
a  temperature  was  reached  at  which  the  waters  of  the  gaseous 
envelope  united  with  the  superficial  rocks  and  led  to  an  aqueo- 
igneous  state.     After  further  cooling  the  second  and  final  con- 
solidation followed,  dating  the  origin  of  the  granites  and  grani- 
tary  rocks.     The  areas  which  cooled  most  rapidly  and  best 
conducted  heat  formed  shallow  oceanic  basins,   whereas   the 
areas  of  poor  conductivity  which  cooled  more  slowly  stood  out 
as  low  continents.     The  internal  heat  of  the  cooling  globe  still 
continues  to  do  its  work,  and  the  cycKc  history  of  its  surface 
is  completed  by  the  erosion  of  rocks,  by  the  accumulation  of 
sediments,  and  by  the  following  subsidence  of  the  areas  loaded 

1  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  191 5,  P-  535- 

2  George  F.  Becker,  letter  of  October  15,  191 5. 


THE  LIFELESS  EARTH 


27 


down  by  these  sediments.  It  appears  that  the  internal  heat 
engine  is  far  more  active  in  the  slowly  cooling  continental  areas 
than  in  the  rapidly  cooling  areas  underlying  the  oceans,  as 
manifested  in  the  continuous  outflows  of  igneous  rocks,  which, 
especially  in  the  early  history  of  the  earth — at  or  before  the 
time  when  life  appeared — covered  the  greater  part  of  the  earth's 
surface.  The  ocean  beds,  being  less  subject  to  the  work  of  the 
internal  heat  engine,  have  always  been  relatively  plane;  except 
near  the  shores,  no  erosion  has  taken  place. 


The  Age  of  the  Earth  and  Beginning  of  the  Life  Period 

The  age  of  the  earth  as  a  solid  body  affords  our  first  in- 
stance of  the  very  wide  discordance  between  physical  and 
biological  opinion.  Among  the  chief  physical  computations 
are  those  of  Lord  Kelvin,  Sir  George  Darwin,  Clarence  King, 
and  Carl  Barus.^  In  1879  Sir  George  Darwin  allowed  56,000,- 
000  years  as  a  probable  lapse  of  time  since  the  earth  parted 
company  wath  the  moon,  and  this  birthtime  of  the  moon  was 
naturally  long  prior  to  that  stage  when  the  earth,  as  a  cool, 
crusted  body,  became  the  environment  of  living  matter.  Far 
more  elastic  than  this  estimate  was  that  of  Kelvin,  who,  in 
1862,  placed  the  age  of  the  earth  as  a  cooling  body  between 
20,000,000  and  400,000,000  years,  with  a  probability  of  98,000,- 
000  years.  Later,  in  1897,  accepting  the  conclusions  of  King 
and  Barus  calculated  from  data  for  the  period  of  tidal  stabiHty, 
Kelvin  placed  the  age  limit  between  20,000,000  and  40,000,000 
years,  a  conclusion  very  unwelcome  to  evolutionists. 

As  early  as  1859  Charles  Darwin  led  the  biologists  in  de- 
manding an  enormous  period  of  time  for  the  processes  of  evo- 

^  Becker,  George  F.,  1910,  p.  5. 


V 


28 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


lution,  being  the  first  to  point  out  that  the  high  degree  of  evo- 
lution and  speciaHzation  seen  in  the  invertebrate  fossils  at  the 
very  base  of  the  Palaeozoic  was  in  itself  a  proof  that  pre-Pateo- 
zoic  evolution  occupied  a  period  as  long  as  or  even  longer  than 
the  post-Paleozoic.  In  1869  Huxley  renewed  this  demand  for 
an  enormous  stretch  of  pre-Palaeozoic  or  pre-Cambrian  time; 
and  as  recently  as  1896  Po^lton^  found  that  400,000,000  years, 
the  greater  limit  of  Kelvin's  original  estimate,  was  none  too 

much. 

Later  physical  computations  greatly  exceeded  this  biological 
demand,  for  in  1908  Rutherford-  estimated  the  time  required 
for  the  accumulation  of  the  radium  content  of  a  uranium  min- 
eral found  in  the  Glastonbury  granitic  gneiss  of  the  Early 
Cambrian  as  no  less  than  500,000,000  years.  This  physical 
estimate  of  the  age  of  the  Early  Cambrian  is  eighteen  times  as 
great  as  that  attained  by  Walcott*^  in  1893  from  his  purely 
geologic  computation  of  the  time  rates  of  deposition  and  max- 
imum thickness  of  strata  from  the  base  of  the  Cambrian  up- 
ward; but  recent  advances  in  our  knowledge  of  the  radioactive 
elements  preclude  the  possibility  of  any  trustworthy  deter- 
mination of  the  age  of  the  elements  through  the  methods  sug- 
gested by  Joly  and  Rutherford. 

We  thus  return  to  the  estimates  based  upon  the  time 
required  for  the  deposition  of  sediments  as  by  far  the  most 
reliable,  especially  for  our  quest  of  the  beginning  of  the  life 
period,  because  erosion  and  sedimentation  imply  conditions  of 
the  earth,  of  the  water,  and  of  the  atmosphere  more  or  less 
comparable  to  those  under  which  life  is  known  to  exist.  These 
geologic  estimates,  which  begin  with  that  of  John  Phillips  in 
i860,  may  be  tabulated  as  follows: 


1  Poulton,  Edward  B.,  1896,  p.  808. 
3  Walcott,  Charles  D.,  1893,  p.  675. 


2  Rutherford,  Sir  Ernest,  1906,  p.  189. 


THE  LIFELESS   EARTH 


29 


Estimates  of  Time  Required  for  the  Processes  of  Past  Deposition  and 
Sedimentation  at  Rates  Similar  to  Those  Observed  at 

the  Present  Day  ^ 


i860. 
i8qo. 
1893. 


1899. 


1Q09. 


John  Phillips 38-96  million  years. 

De  Lapparent 67-90  million  years. 

Walcott 55-  70  million  years. 

(27,640,000  years  since  the  base  of  the  Cam- 
brian Palaeozoic;  17,500,000  years  or  up- 
ward for  the  pre-Palaeozoic.) 

Qgjj^jg 100-400  million  years. 

(Minimum  100  million  years;  maximum — 
slowest  known  rates  of  deposition  —  400 
million  years.) 

Sollas 34-80  million  years. 

(The  larger  estimate  of  80  million  years  on  the 
theory  that  pre-Palaeozoic  sediments  took 
as  much  time  as  those  from  the  base  of 
the  Cambrian  upward,  allowing  for  gaps 
in  the  stratigraphic  column.) 


These  estimates  give  a  maximum  of  sixty-four  miles  as  the 
total  accumulation  of  sedimentary  rocks,  which  is  equivalent 
to  a  layer  2,300  feet  thick  over  the  entire  face  of  the  earth.^ 
From  these  purely  geologic  data  the  time  ratio  of  the  entire 
life  period  is  now  calculated  in  terms  of  millions  of  years, 
assuming  the  approximate  reliability  of  the  geologic  time  scale. 
The  actual  amount  of  rock  weathered  and  deposited  was  prob- 
ably far  greater  than  that  which  has  been  preserved. 

In  general,  these  estimates  are  broadly  concordant  with 
those  reached  by  an  entirely  different  method,  namely,  the 
amount  of  sodium  chloride  (common  salt)  contained  in  the 
ocean,^  to  understand  which  we  must  first  take  another  glance 
at  the  geography  and  chemistry  of  the  primordial  earth. 

The  lifeless  primordial  earth  can  best  be  imagined  by  look- 
ing at  the  lifeless  surface  of  the  moon,  featured  by  volcanic 

1  Becker,  George  F.,  1910,  pp.  2,  3,  5. 

2  Clarke,  F.  W.,  19 16,  p.  30- 

'See  Salt  as  a  Measure  of  the  Age  of  the  Ocean,  p.  35. 


30 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


action  with  little  erosion  or  sedimentation  because  of  the  lack 
of  water. 

The  surface  of  the  earth,  then,  was  chiefly  spread  with 
granitic  masses  known  as  batholiths  and  with  the  more  super- 
ficial volcanic  outpourings.     There  were  volcanic  ashes;  there 


Fig.  I.     The  Moon's  Surface. 

"  The  lifeless  primordial  earth  can  best  be  imagined  by  looking  at  the  lifeless  surface  of 
the  moon."  A  portion  of  the  moon's  surface,  many  miles  in  diameter,  illuminated 
by  the  rising  or  setting  sun  and  showing  the  craters  and  areas  of  lava  outflow.  The 
Meteor  Crater  of  Arizona,  formerly  known  as  Coon  Butte — a  huge  hole,  4,500  feet  in 
diameter  and  600  feet  in  depth,  made  by  a  falling  meteorite — is  strikingly  similar  to 
these  lunar  craters  and  suggests  the  possibility  that,  instead  of  being  the  result  of 
volcanic  action,  the  craters  of  the  moon  may  have  been  formed  by  terrific  impacts  of 
meteoric  masses.     Photograph  from  the  Mt.  Wilson  Observatory. 

were  gravels,  sands,  and  micas  derived  from  the  granites;  there 
were  clays  from  the  dissolution  of  granitic  feldspars;  there  were 
loam  mixtures  of  clay  and  sand;  there  was  gypsum  from  min- 
eral springs. 

Bare  rocks  and  soils  were  inhospitable  ingredients  for  any 
but  the  most  rudimentary  forms  of  life  such  as  were  adapted 
to  feed  directly  upon  the  chemical  elements  and  their  simplest 


THE  LIFELESS   EARTH 


31 


compounds,  or  to  transform  their  energy  without  the  friendly 
aid  of  sunshine.     The  only  forms  of  life  to-day  which  can  exist\ 
in  such  an  inhospitable  environment  as  that  of  the  lifeless 
earth  are  certain  of  the  simplest  bacteria,  which,  as  we  shall/ 
see,  feed  directly  upon  the  chemical  elements. 

It  is  interesting  to  note  that,  in  the  period  when  the  sun's 
light  was  partly  shut  off  by  watery  and  gaseous  vapors,  the 
early  volcanic  condition  of  the  eartli^s  surface  may  have  supplied 
life  with  fundamentally  important  chemical  elements,  as  well 
as  with  the  heat-energy  of  the  waters  or  of  the  soils.  Volcanic 
emanations  contain^  free  hydrogen,  both  oxides  of  carbon,  and 
frequently  hydrocarbons  such  as  methane  (CH4)  and  ammo- 
nium chloride:  the  last  compound  is  often  very  abundant. 
Volcanic  waters  sometimes  contain  ammonium  (NH4)  salts^ 
from  which  life  may  have  derived  its  first  nitrogen  supply. 
For  example,  in  the  DeviFs  Inkpot,  Yellowstone  Park,  ammo- 
nium sulphate  forms  ^2>  P^^  ^^^^  of  the  dissolved  saline  matter: 
it  is  also  the  principal  constituent  of  the  mother  liquor  of  the 
boric  fumaroles  of  Tuscany,  after  the  boric  acid  has  crystallized 
out.  A  hot  spring  on  the  margin  of  Clear  Lake,  California, 
contains  107.76  grains  per  gallon  of  ammonium  bicarbonate. 

There  were  absent  from  the  primordial  earth  the  greater 
part  of  the  fine  sediments  and  detrital  material  which  now 
cover  three-fourths  of  its  surface,  and  from  which  a  large  part 
of  the  sodium  content  has  been  leached.  The  original  surface 
of  the  earth  was  thus  composed  of  granitic  and  other  igneous 
rocks  to  the  exclusion  of  all  others,-  the  essential  constituents 
of  these  rocks  being  the  lime-soda  feldspars  from  which  the 
sodium  of  the  ocean  has  since  been  leached.  Waters  issuing 
from  such  rocks  are,  as  a  rule,  relatively  richer  in  silica  than 

» Clarke,  F.  W.,  1916,  chap.  VIII.,  also  pp.  197,  199,  243,  244. 
*  Becker,  George  F.,  1910,  p.  12. 


32 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


Fig.  2. 


waters  issuing  from  modern  sedimentary  areas.  They  thus 
furnish  a  favorable  environment  for  the  development  of  such 
low  organisms  (or  their  ancestors)  as  the  existing  diatoms, 
radiolarians,  and  sponges,  which  have  skeletons  composed  of 

hydrated    silica,    mineralogi- 
cally  of  opal. 

The  decomposition  and 
therefore  the  erosion  of  the 
massive  rocks  was  slower  then 
than  at  present,  for  none  of 
the  life  agencies  of  bacteria, 
of  algae,  of  lichens,  and  of  the 
higher  plants,  which  are  now 
at  work  on  granites  and  vol- 
canic rocks  in  all  the  humid 
portions  of  the  earth,  had  yet 
appeared.  On  the  other  hand, 
much  larger  areas  of  these 
rocks  were  exposed  than  at 
present. 

In  brief,  to  imagine  the 
primal  lifeless  earth  we  must 
subtract  all  those  portions  of 
mineral  deposits  which  as  they 
exist  to-day  are  mainly  of  organic  origin,  such  as  the  organic  car- 
bonates and  phosphates  of  lime,^  the  carbonaceous  shales  as  well 
as  the  carbonaceous  limestones,  the  graphites  derived  from  car- 
bon, the  silicates  derived  from  diatoms,  the  iron  deposits  made 

^  It  seems  improbable  that  organisms  originally  began  to  use  carbon  or  phosphorus 
in  elementary  form:  carbonates  and  phosphates  were  probably  available  at  the  very  l^e- 
ginning  and  resulted  from  oxidations  or  decompositions, — W.  J.  Gies. 

Phosphate  of  lime,  apatite,  is  an  almost  ubiquitous  component  of  igneous  rocks,  but 
in  very  small  amount.  In  more  than  a  thousand  analyses  of  such  rocks,  the  average 
percentage  of  PjOs  is  0.25  per  cent. — F.  W.  Clarke. 


Deep-Sea  Ooze,  the  Foramt- 

NIFERA. 


Photograph  of  a  small  portion  of  a  cal- 
careous deposit  on  the  sea  bottom  formed 
by  the  dropping  down  from  the  sea  sur- 
face of  the  dead  shells  of  foraminifera, 
chiefly  Glohigerina,  greatly  magnified. 
Such  calcareous  deposits  extend  over 
large  areas  of  the  sea  bottom.  Repro- 
duced from  The  Depths  of  the  Ocean,  by 
Sir  John  Murray  and  Doctor  Johan 
Hjort  by  permission  of  the  Macmillan 
Company. 


THE  LIFELESS   EARTH 


33 


by  bacteria,  the  humus  of  the  soil  containing  organic  acids, 
the  soil  derived  from  rocks  which  are  broken  up  by  bacteria, 
and  even  the  ooze  from  the  ocean  floor,  both  calcareous  and 

TABLE  I 

Average  Distribution  of  the  Chemical  Elements  in  Earth,  Air,  and 

Water  at  the  Present  Time  ^ 

{Life  Elements  in  Italics) 


Oxygen 


Silicon 

Aluminum. 

Iron 

Calcium. . .  . 
Magnesium. 

Sodium 

Potassium.  . 
Hydrogen . . . 
Titanium  . . 

Carbon 

Chlorine . . . . 
Bromine. . . 
Phosphorus . 
Sulphur. .  . 
Barium. .  . . 
Manganese. 
Strontium. 
Nitrogen . . . 


The  Rocks, 
Lithosphere, 
Q3  per  cent 


Fluorine 

All  other  elements 


47-33 


27.74 

785 

450 

3-47 
2.  24 

2.46 

2.46 

.22 

.46 
.19 
.06 

.  12 
.12 
.08 
.08 
.02 


The  Waters, 

Hydrosphere, 

7  per  cent 


8579 


•05 

•14 
I.  14 

.04 

10.67 


.002 

2  .07 
.008 


The  Atmosphere 


Average, 

Including 

Atmosphere 


20.8 

(variable  to  some 
extent) 


10 
50 


09 


variable 


variable 


78.0 

(variable  to  some 

extent) 


50.02 


25.80 

730 
4.18 

3.22 

2.08 
2 .36 
2.28 

■95 
•43 
.18 

.20 

.  II 
.11 

.08 
.08 
.02 

•03 


10 

47 


silicious,  formed  from  the  shells  of  foraminifera  and  the  skele- 
tons of  diatoms.  Thus,  before  the  appearance  of  bacteria,  of 
algte,  of  foraminifera,  and  of  the  lower  plants  and  lowly  inver- 
tebrates, the  surface  of  the  earth  was  totally  different  from 


» Clarke,  F.  VV.,  1916,  p.  34. 


34 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


what  it  is  at  present;  and  thus  the  present  chemical  composi- 
tion of  terrestrial  matter,  of  the  sea,  and  of  the  air,  as  indi- 
cated by  Table  I,  is  by  no  means  the  same  as  its  primordial 
composition  80.000,000  years  ago. 

In  Table  I  all  the  chemical  ^Mife  elements'^  which  enter 
more  or  less  freely  into  organic  compounds  are  indicated  by 
italics,  showing  that  life  has  taken  tip  and  made  use  of  practically 
all  the  chemical  elements  of  frequent  occurrence  in  the  rocks, 
waters,  and  air,  with  the  exception  of  aluminum,  barium,  and 
strontium,  which  are  extremely  rare  in  life  compounds,  and 
of  titanium,  which  thus  far  has  not  been  found  in  any.  But 
even  these  elements  appear  in  artificial  organic  compounds, 
showing  combining  capacity  without  biological  ''inclination'' 
thereto.  In  the  life  compounds,  as  in  the  lithosphere  and 
hydrosphere,  it  is  noteworthy  that  the  elements  of  least  atomic 
weight  (Table  II)  predominate  over  the  heavier  elements. 

Primordial  Environment — The  Lifeless  Water 

According  to  the  nebular  theory  of  Laplace  the  waters 
originated  in  the  primordial  atmosphere;  according  to  the 
planetesimal  theory  of  Chamberlin^  and  Moulton,'-  the  greater 
volume  of  water  has  been  gradually  added  from  the  interior 
of  the  earth  through  the  vaporous  discharges  of  hot  springs. 
As  Suess  observes:  ''The  body  of  the  earth  has  given  forth  its 
ocean.'^ 

From  the  beginning  of  Archaeozoic  time,  namely,  back  to  a 
period  of  80,000,000  years,  we  have  little  biologic  or  geologic 
evidence  as  to  the  stability  of  the  earth.  From  the  beginning 
of  the  Palaeozoic,  namely,  for  the  period  of  the  last  30,000,000 
years,  the  earth  has  been  in  a  condition  of  such  stability  that 


^  Chamberlin,  Thomas  Chrowder,  1916. 


Moulton,  F.  R.,  191 2,  p.  244. 


THE  LIFELESS  WATER 


35 


the  oceanic  tides  and  tidal  currents  were  similar  to  those  of  the 
present  day;  for  the  early  strata  are  full  of  such  evidences  as 
ripple  marks,  beach  footprints,  and  other  proofs  of  regularly 
recurrent  tides.  ^ 

As  in  the  case  of  the  earth,  the  chemistry  of  the  lifeless 
primordial  seas  is  a  matter  of  inference,  i.  e.,  of  subtraction  of 
those  chemical  elements  which  have  been  added  as  the  infant 
earth  has  grown  older.  The  relatively  simple  chemical  con- 
tent of  the  primordial  seas  must  be  inferred  by  deducting  the 
mineral  and  organic  products  which  have  been  sweeping  into 
the  ocean  from  the  earth  during  the  last  80,000,000  to  90,000,000 
years;  and  also  by  deducting  those  that  have  been  precipitated 
as  a  result  of  chemical  reactions,  calcium  chloride  reacting  with 
sodium  phosphate,  for  example,  to  yield  precipitated  calcium 
phosphate  and  dissolved  sodium  chloride.-  The  present  waters 
of  the  ocean  are  rich  in  salts  which  have  been  derived  by  solu- 
tion from  the  rocks  of  the  continents. 

Thus  we  reach  our  first  conclusion  as  to  the  origin  of  life, 
namely:  it  is  probable  that  life  originated  on  the  continents, 
either  in  the  moist  crevices  of  rocks  or  soils,  in  the  fresh  waters 
of  continental  pools,  or  in  the  slightly  saline  waters  of  the 
bordering  primordial  seas. 


Salt  as  a  Measure  of  the  Age  of  the  Ocean 

As  long  ago  as  17 15  Edmund  Halley  suggested  that  the 
amount  of  salt  in  the  ocean  might  afford  a  means  of  computing 
its  age.  Assuming  a  primitive  fresh-water  ocean,  Becker^  in 
1 9 10  estimated  its  age  as  between  50,000,000  and  70,000,000 
years,  probably  closer  to  the  upper  limit.  The  accumulation 
of  sodium  was  probably  more  rapid  in  the  early  geologic  periods 


^  Becker,  George  F.,  1910,  p.  18. 

*  Becker,  George  F.,  1910,  pp.  16,  17. 


2  W.  J.  Gies. 


36 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


than  at  the  present  time,  because  the  greater  part  of  the  earth's 
surface  was  covered  with  the  granitic  and  igneous  rocks  which 
have  since  been  largely  covered  or  replaced  by  sedimentary 
rocks,  a  diminution  causing  the  sodium  content  from  the  earth 
to  be  constantly  decreasing.^  This  is  on  the  assumption  that 
the  primitive  ocean  had  no  continents  in  its  basins  and  that  the 
continental  areas  were  not  much  greater  than  at  the  present 
time,  namely,  20.6  per  cent  to  25  per  cent  of  the  surface  of 
the  globe. 

Age  of  the  Ocean  Calculated  from  its  Sodium  Content* 


1876.  T.  Mellard  Reade. 

1899.  J.  Joly 80-  90  million  years. 

1900.  J.  Joly 90-100  million  years. 

1909.  Sollas 80-150  million  years. 

1910.  Becker 50-  70  million  years. 

1911.  F.  W.  Clarke  and  Becker 94,712,000  years. 

191 5.  Becker 60-100  million  years. 

1916.  Clarke somewhat  less  than  loo  million  years. 


From  the  mean  of  the  foregoing  computations  it  is  inferred 
that  the  age  of  the  ocean  since  the  earth  assumed  its  present 
form  is  somewhat  less  than  100,000,000  years,  '^he  63,000,000 
tons  of  sodium  which  the  sea  has  received  yearly  by  solution 
from  the  rocks  has  been  continually  uniting  with  its  equivalent 
of  chlorine  to  form  the  salt  (NaCl)  of  the  existing  seas.^  So 
with  the  entire  present  content  of  the  sea,  its  sulphates  as  well 
as  its  chlorides  of  sodium  and  of  magnesium,  its  potassium,  its 
calcium  as  well  as  those  rare  chemical  elements  which  occasion- 
ally enter  into  the  life  compounds,  such  as  copper,  fluorine, 
boron,  barium — all   these  earth-derived   elements  were  much 

*  Becker,  George  F.,  1915,  p.  201;  1910,  p.  12. 

2  After  Becker,  George  F.,  19 10,  pp.  3-5;  and  Clarke,  F.  W.,  19 16,  pp.  150,  152. 

3  Becker,  George  F.,  1910,  pp.  7,  8,  10,  12. 


THE  LIFELESS   WATER 


37 


rarer  in  the  primordial  seas  than  at  the  present  time.  Yet 
from  the  first  the  air  in  sea-water  was  much  richer  in  oxygen 
than  the  atmosphere.^ 

As  compared  with  primordial  sea- water,  which  was  relatively 
fresh  and  free  from  salts  and  from  nitrogen,  existing  sea-water 
is  an  ideal  chemical  medium  for  life.  As  a  proof  of  the  special 
adaptability  of  existing  sea-water  to  present  biochemical  con- 
ditions, a  very  interesting  comparison  is  that  between  the 
chemical  composition  of  the  chief  body  fluid  of  the  highest 
animals,  namely,  the  blood  serum,  and  the  chemical  composi- 
tion of  sea-water,  as  given  by  Henderson.'- 


Chemical  Composition  of  Present  Sea- Water  and  of  Blood  Serum 


*' Li/e  EJemenis" 

Sodium 

Magnesium  

Calcium     

Potassium 

ClUorine       

SO4  (sulphur  tetroxide) 

CO3  (carbon  trioxide) 

Bromine 

P2O5  (phosphorous  pentoxide) 


In  Sea-Water 


30.59 

3-79 
1 .  20 

I.  II 

55-27 
7.66 
o.  21 
o.  19 


In  Blood  Serum 


390 
0.4 
I  .0 
2.7 

450 
12  .0 

0.4 


Primordial  Chemical  Environment 

Since  the  primal  sea  was  devoid  of  those  earth-borne  nitro- 
gen compounds  which  are  indirectly  derived  first  from  the 
atmosphere  and  then  from  the  earth  through  the  agency  of  the 
nitrifying  bacteria,  those  who  hold  to  the  hypothesis  of  the 
marine  origin  of  protoplasm  fail  to  account  for  the  necessary 
proportion  of  nitrogenous  matter  there  to  begin  with. 


'  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  1915,  p.  84. 
-  Henderson,  Lawrence  J.,  1913,  p.  187. 


38 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


When  we  consider  that  those  chemical  '^hfe  elements" 
which  are  most  essential  to  living  matter  were  for  a  great  period 
of  time  either  absent  or  present  in  a  highly  dilute  condition  in 
the  ocean,  it  appears  that  we  must  abandon  the  ancient  Greek 
conception  of  the  origin  of  life  in  the  sea,  and  reaffirm  our 
conclusion  that  the  lowliest  organisms  originated  either  in 
moist  earths  or  in  those  terrestrial  waters  which  contained 
nitrogen.  Nitrate  and  nitrite  occasionally  arise  from  the  union 
of  nitrogen  and  oxygen  in  electrical  discharges  during  thunder- 
storms, and  were  presumably  thus  produced  before  life  began. 
These  and  related  nitrogen  compounds,  so  essential  for  the 
development  of  protoplasm,  may  have  been  specially  concen- 
trated in  pools  of  water  to  degrees  particularly  favorable  for  the 
origin  of  proto plasm }-=^. 

It  appears,  too,  that  every  great  subsequent  higher  life 
phase — the  bacterial  phase,  the  chlorophyllic  algal  phase,  the 
protozoan  phase — was  also  primarily  of  fresh-water  and  sec- 
ondarily of  marine  habitat.  From  terrestrial  waters  or  soils 
life  may  have  gradually  extended  into  the  sea.  It  is  probable 
that  the  succession  of  marine  forms  was  itself  determined  to 
some  extent  by  adaptation  to  the  increasing  concentration  of 
saline  constituents  in  sea-water.  That  the  invasion  of  the  sea 
upon  the  continental  areas  occurred  at  a  very  early  period  is 
demonstrated  by  the  extreme  richness  and  profusion  of  marine 
life  at  the  base  of  the  Cambrian. 

That  life  originated  in  water  (H2O)  there  can  be  little  doubt, 
hydrogen  and  oxygen  ranking  as  primary  elements  with  nitro- 
gen. The  fitness  of  water  to  life  is  maximal-  both  as  a  solvent 
in  all  the  bodily  fluids,  and  as  a  vehicle  for  most  of  the  other 
chemical  compounds.     Further,  since  water  itself  is  a  solvent 

*  Suggested  by  Professor  W.  J: -Gies. 

-  These  notes  upon  water  are  chiefly  from  the  very  suggestive  treatise,  **The  Fitness 
of  the  Environment,"  by  Henderson,  Lawrence  J.,  1913. 


/ 


/ 


/ 


t 


THE  ATMOSPHERE 


39 


that  fails  to  react  with  many  substances  (with  nearly  all  bio- 
logical substances)  it  serves  also  as  a  factor  of  biochemical 
stability. 

In  relation  to  the  application  of  our  theory  of  action,  re- 
action, and  interaction  to  the  processes  of  life,  the  most  im- 
portant property  of  water  is  its  electric  property,  known  as 
the  dielectric  constant.  Although  itself  only  to  a  slight  degree 
dissociated  into  ions,  it  is  the  bearer  of  dissolved  electrolytic 
substances  and  thus  possesses  a  high  power  of  electric  conduc- 
tivity, properties  of  great  importance  in  the  development  of  the 
electric  energy  of  the  molecules  and  atoms  in  ionization.  Thus 
water  is  the  very  best  medium  of  electric  ionization  in  solution, 
and  was  probably  essential  to  the  mechanism  of  life  from  its 
very  origin.^ 

Through  all  the  electric  changes  of  its  contained  solvents 
water  itself  remains  very  stable,  because  the  molecules  of 
hydrogen  and  oxygen  are  not  easily  dissociated;  their  union 
in  water  contributes  to  the  living  organism  a  series  of  proper- 
ties which  are  the  prime  conditions  of  all  physiological  and 
functional  activity.  The  great  surface  tension  of  water  as 
manifested  in  capillary  action  is  of  the  highest  importance  to 
plant  growth;  it  is  also  an  important  force  acting  within  the 
formed  colloids,  the  protoplasmic  substance  of  life. 

Primordial  Environment — The  Atmosphere 

It  is  significant  that  the  simplest  known  living  forms  derive  ^ 
their  chemical  ''life  elements"  partly  from  the  earth,  partly 
from  the  water,  and  partly  from  the  atmosphere.     This  was 
not  improbably  true  also  of  the  earliest  living  forms. 

One   of   the   mooted   questions   concerning   the  primordial 

^  Henderson,  Lawrence  J.,  1913,  p.  256. 


40 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


atmosphere^  is  whether  or  no  it  contained  free  oxygen.  The 
earHest  forms  of  Hfe  were  probably  dependent  on  atmospheric 
oxygen,  although  certain  existing  bacterial  organisms,  known 
as  '*  anaerobic,^'  are  now  capable  of  existing  without  it. 

The  primordial  atmosphere  was  heavily  charged  with  water 
vapor  (H2O)  which  has  since  been  largely  condensed  by  cooling. 
In  the  early  period  of  the  earth's  history  volcanoes-  were  also 
pouring  into  the  atmosphere  much  greater  amounts  of  car- 
bon dioxide  (CO2)  than  at  the  present  time.  At  present  the 
amount  of  carbon  dioxide  in  the  atmosphere  averages  about 
three  parts  in  10,000,  but  there  is  little  doubt  that  the  primor- 
dial atmosphere  was  richer  in  this  compound,  which  next  to 
water  and  nitrogen  is  by  far  the  most  important  both  in  the 
origin  and  in  the  development  of  living  matter.  The  atmos- 
pheric carbon  dioxide  is  at  present  continually  being  withdrawn 
by  the  absorption  of  carbon  in  living  plants  and  the  release  of 
free  oxygen;  it  is  also  washed  out  of  the  air  by  rains.  On  the 
other  hand,  the  respiration  of  animals,  the  combustion  of  car- 
bonaceous matter,  and  the  discharges  from  volcanoes  are  con- 
tinually returning  it  to  the  air  in  large  quantities. 

As  to  carbon,  from  our  present  knowledge  we  cannot  con- 
ceive  of  organisms  that  did  not  consist,  from  the  instant  of 
initial  development,  of  protoplasm  containing  hydrogen,  oxygen, 
nitrogen,  and  carbon.  Probably  carbon  dioxide,  the  most  likely 
source  of  carbon  from  the  beginning,  was  reduced  in  the  pri- 
mordial environment  by  other  than  chlorophyllic  agencies,  by 
simple  chemical  influences. 

Since  carbon  is  a  less  dominant  element^  than  nitrogen  in 
the  Hfe  processes  of  the  simplest  bacteria,  we  cannot  agree 
with  the  theory  that  carbon  dioxide  was  coequal  with  water 

^  Becker,  George  F.,  letter  of  October  15,  1915. 
-  Henderson,  Lawrence  J.,  1913,  p.  134. 
3  Jordan,  Edwin  O.,  1908,  p.  66. 


THE  ATMOSPHERE 


41 


as  a  primary  compound  in  the  origin  of  life;  it  probably  was 
more  widely  utilized  after  the  chlorophyllic  stage  of  plant 
evolution,  for  not  until  chlorophyll  appeared  was  life  equipped 
with  the  best  means  of  extracting  large  quantities  of  carbon 
dioxide  from  the  atmosphere. 

The  stable  elements  of  the  present  atmosphere,  for  which 
alone  estimates  can  be  given,  are  essentially  as  follows:^ 


Oxygen . . 
Nitrogen 
Argon . . . 


By  Weight 


23.024 

75-539 
1-437 

100.000 


By  Volume 

20 

941 

78 

122 

937 

100.000 


Atmospheric  carbon  dioxide  (CO2),  which  averages  about  three 
parts  in  every  10,000,  and  water  (H2O)  are  always  present 
in  varying  amounts;  besides  argon,  the  rare  gases  helium, 
xenon,  neon,  and  krypton  are  present  in  traces.  None  of  the 
rare  gases  which  have  been  discovered  in  the  atmosphere,  such 
as  helium,  argon,  xenon,  neon,  krypton,  and  niton — the  latter 
a  radium  emanation — are  at  present  known  to  have  any  rela- 
tion to  the  life  processes.  Carbon  dioxide-  exists  in  the  atmos- 
phere as  an  inexhaustible  reservoir  of  carbon,  only  slightly 
depleted  by  the  drafts  made  upon  it  by  the  action  of  chloro- 
phyllic plants  or  by  its  solution  in  the  waters  of  the  conti- 
nents and  oceans.  Soluble  in  water  and  thus  equally  mobile, 
of  high  absorption  coefficient,  and  of  universal  occurrence, 
it  constitutes  a  reservoir  of  carbon  for  the  development  of 
plants  and  animals,  radiant  energy  being  required  to  make  this 
carbon  available  for  biological  use.     Carbon  dioxide  in  water 

*  Clarke,  F.  W.,  letter  of  March  7,  1916. 

2  Henderson,  Lawrence  J.,  1913,  pp.  136-139. 


I 


I 


42 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


I 


forms  carbonic  acid,  one  of  the  few  instances  of  biological 
decomposition  of  water.  This  compound  is  so  unstable  that  it 
has  never  been  obtained.  Carbon  dioxide  is  derived  not  only 
through  chlorophyllic  agencies  by  means  of  free  oxygen,  but 
also  by  the  action  of  certain  anaerobic  bacteria  and  moulds 
without  the  presence  of  free  oxygen,  as,  for  example,  through 
the  catalytic  action  of  zymase,  the  enzyme  of  yeast,  wh'ich  is 
soluble  in  water.  Loeb^  dwells  upon  the  importance  of  the 
bicarbonates  as  regulators  in  the  development  of  the  marine 
organisms  by  keeping  neutral  the  water  and  the  solutions  in 
which  marine  animals  live.  Similarly  the  life  of  fresh-water 
animals  is  also  prolonged  by  the  addition  of  bicarbonates. 

*  Loeb,  Jacques,  1906,  pp.  96,  97. 


4 


i 


CHAPTER  II 

THE  SUN  AND  THE  PHYSICOCHEMICAL  ORIGINS 

OF  LIFE 

Heat  and  light.  Chemical  "  life  elements"  as  they  exist  in  the  sun.  Primor- 
dial environment — electric  energy  and  the  sun's  heat.  Capture  of  the 
energy  of  sunlight.  Action  and  reaction  as  adaptive  properties  of  the 
Kfe  elements.  Interaction  or  coordination  of  the  properties  of  the  life 
elements.  Adaptation  in  the  colloidal  state.  Cosmic  properties  and  life 
functions  of  the  chief  chemical  life  elements.  Pure  speculation  as  to  the 
primary  physicochemical  stages  of  life.  Evolution  of  actions  and  reac-  . 
tions.     Evolution  of  interactions.     New  organic  compounds. 

• 

We  will  now  consider  the  sun  as  the  source  of  heat,  light, 
and  other  forms  of  energy  which  conditioned  the  origin  of  life. 

.  Heat  and  -Light 

It  IS  possible  that  in  the  earher  stages  of  the  earth's  history 
the  sun's  light  and  heat  may  have  been  different  in  amount  from 
what  they  are  at  present;  so  far  as  can  be  judged  from  the 
available  data  it  seems  probable  that,  if  perceptibly  different,  • 
they  were  greater  then  than  now.  But  if  they  were  greater, 
the  atmosphere  must  have  been  more  full  of  clouds — as  that  of 
Venus  apparently  is  to-day — and  have  reflected  away  into  space 
much  more  than  the  45  per  cent  of  the  incident  radiation  which 
it  reflects  at  present.  On  the  earth's  surface,  beneath  the  cloud 
layer,  the  temperature  need  not  have  been  much  higher  than 
the  present  mean  temperature,  but  was  doubtless  much  more 
equable,  with  more  moisture,  while  the  amount  of  sunlight 
reaching  the  earth's  surface  may  have  been  less  intense  and 
continuous  than  at  present. 

43 


44 


THE  ORIGIN-  AND  EVOLUTION  OF  LIFE 


The  following  are  among  the  reasons  why  the  primordial 
solar  influences  upon  the  earth  may  have  differed  from  the 
present  solar  influences.  It  appears  probable  that  the  lifeless 
surface  of  the  primordial  earth  was  like  that  of  the  moon — 
covered  not  only  with  igneous  rocks  but  with  piles  of  heat-stor- 


HEAT     LIGJ 


CHEMIC4L 


Billion  vtbrati 


INFRA    RED 


ABC   D 


ULTRA   VIOLET 


Fig.  3.    Light,  Heat,  and  Chemical  Influence  of  the  Sun. 

Diagram  showing  how  the  increase,  maximum,  and  decrease  of  heat,  light,  and  chemical 
energy  derived  from  the  sun  correspond  to  the  velocity  of  the  vibrations.     After  Ulric 


Dahlgren. 


ing  debris,  as  recently  described  by  Russell ' — and  if,  like  the 
moon,  the  earth  had  had  no  atmosphere,  then  the  reflecting 
power  of  its  surface  would  have  represented  a  loss  of  only  40 
per  cent  of  the  sun's  heat.  Sut  a  large  amount  of  aqueous 
vapor  and  of  carbon  dioxide  in  the  primordial  atmosphere  prob- 
ably served  to  form  an  atmospheric  blanket  which  inhibited 
the  radiation  from  the  earth's  surface  of  such  solar  heat  as  pen- 
etrated to  it,  and  also  prevented  excessive  changes  of  temper- 
ature. Thus  there  was  on  the  primal  earth  a  greater  reg- 
ularity of  the  sun's  heat-supply,  with  more  moisture. 

1  Russell,  H.  N.,  1916,  p.  75. 


LIFE   ELEMENTS   IN  THE   SUN 


45 


To  sum  up,  if  the  primordial  atmosphere  contained  more 
aqueous  \^apor  and  carbon  dioxide  than  at  present,  the  greater 
cloudiness  of  the  atmosphere  would  have  very  considerably  in- 
creased the  albedo,  that  is,  the  reflection  of  solar  heat,  as  well 
as  hght,  away  into  space.  If  the  earth's  surface  was  covered 
with  loose  debris,  it  would  have  retained  more  of  the  solar  heat 
which  reached  it  directly;  but,  with  such  an  atmosphere  as  is 
postulated,  very  little  of  the  solar  radiation  would  have  reached 
the  surface  directly.  What  is  true  of  the  indirect  access  of  the 
supply  of  light  from  the  sun  would  also  be  true  of  the  supply 
of  heat.  On  the  other  hand,  the  greater  blanketing  power  of 
the  atmosphere  would  tend  to  keep  the  surface  as  warm  as  it 
is  now,  in  spite  of  the  smaller  direct  supply  of  heat. 

It  is  also  possible  that,  through  the  agency  of  thermal 
springs  and  the  heat  of  volcanic  regions,  primordial  life  forms 
may  have  derived  their  energy  from  the  heat  of  the  earth  as 
well  as  from  that  of  the  sun.  This  is  in  general  accord  with 
the  fact  that  the  most  primitive  organisms  surviving  upon  the 
earth  to-day,  the  bacteria,  are  dependent  upon  heat  rather 
than  upon  light  for  their  energy. 

We  have  thus  far  observed  that  the  primal  earth,  air,  and 
water  contained  all  the  chemical  elements  and  three  of  the 
most  simple  but  important  chemical  compounds,  namely, 
water,  nitrates,  and  carbon  dioxide,  which  are  known  to  be 
essential  to  the  bacterial  or  prechlorophyllic,  and  algal  and 
higher  chlorophyllic  stages  of  the  life  process. 

Chemical  ''Life  Elements"  as  They  Exist  in  the  Sun 


An  initial  step  in  the  origin  of  life  was  the  coordination  or 
bringing  together  of  these  elements  which,  so  far  as  we  know, 
had  never  been  chemically  coordinated  before  and  which  are 


40 


THE   ORIGIN  AND   EVOLUTION  OF  LIFE 


widely  distributed  in  the  solar  spectrum.  Therefore,  before 
examining  the  properties  of  these  elements,  it  is  interesting  to 
trace  them  back  from  the  earth  into  the  sun  and  thus  into 
the  cosmos.     It  is  through  these  ''properties"  which  in  life 


Fig.  4.    Chemical  Life  F^lements  in  the  Sun. 

Three  regions  of  the  solar  spectrum  with  lines  showing  the  presence  of  such  essential  life 
elements  as  carbon,  nitrogen,  calcium,  iron,  magnesium,  sodium,  and  hydrogen.  From 
the  Mount  Wilson  Observatory. 

subserve  ''functions"  and  "adaptations"  that  all  forms  of  life, 
from  monad  to  man,  are  linked  with  the  universe. 

Excepting  hydrogen  and  oxygen,  the  principal  elements 
which  enter  into  the  formation  of  living  protoplasm  are  minor 
constituents  of  the  mass  of  matter  sown  throughout  space  in 
comparison  with  the  rock-forming  elements.^  Again  excepting 
hydrogen,  their  lines  in  the  solar  spectrum  are  for  the  most 

1  Russell,  Henry  Norris,  letter  of  March  6,  1916. 


LIFE   ELEMENTS   IN  THE   SUN 


47 


part  weak,  and  only  shown  on  high  dispersion  plates,  while 
hydrogen  is  represented  by  very  strong  lines,  as  shown  by 
spectroheliograms  of  solar  prominences.  The  Hnes  of  oxygen 
are  relatively  faint;  it  appears  principally  as  a  compound, 
titanium  oxide  (Ti02)  in  sun-spots,  although  a  triple  line  in  the 
extreme  red  seems  also  to  be  due  to  it.  In  the  chromosphere, 
or  higher  atmosphere  of  the  sun,  hydrogen  is  not  in  a  state  of 
combustion,  and  the  fine  hydrogen  prominences  show  radia- 
tions comparable  to  those  in  a  vacuum  tube.^ 

Nitrogen,  the  next  most  important  life  element,  is  displayed 
in  the  so-called  cyanogen  bands  of  the  ultra-violet,  made  visible 
by  high-dispersion  photographs. 

Carbon  is  shown  in  many  Hnes  in  green,  which  are  relatively 
bright  near  the  sun's  edge;  it  is  also  present  in  comets,  and 
carbonaceous  meteorites  (Orgueil,  Kold  Bokkeveld,  etc.)  are 
well  known.     Graphite  occurs  in  meteoric  irons. 

In  the  solar  spectrum  so  far  as  studied  no  Hnes  of  the  "life 
elements,"  phosphorus,  sulphur,  and  chlorine,  have  been  de- 
tected. On  the  other  hand,  the  metaHic  elements  which  enter 
into  the  Hfe  compounds,  iron,  sodium,  and  calcium,  are  aU 
represented  by  strong  lines  in  the  solar  spectrum,  the  excep- . 
tion  being  potassium  in  which  the  lines  are  faint.  Of  the  eight 
metallic  elements  which  are  most  abundant  in  the  earth's  crust, 
as  weU  as  the  non-metaUic  elements  carbon  and  silicon,  six 
are  also  among  the  eight  strongest  in  the  solar  spectrum.  In 
general,  however,  the  important  life  elements  are  very  widely 
distributed  in  the  stellar  universe,  showing  most  prominently 
in  the  hotter  stars,  and  in  the  case  of  hydrogen  being  uni- 
versal. 

We  have  now  considered  the  source  of  four  "life  elements," 
namely,  hydrogen,  oxygen,  nitrogen,  and  carbon,  also  the 

^  Hale,  George  Ellery,  letter  of  March  10,  19 16. 


48  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

presence  in  the  sun  and  stars  of  the  metallic  elements.  Before 
passing  to  the  properties  of  these  and  other  life  elements  let  us 
consider  how  lifeless  energy  is  transformed  into  living  energy. 

Primordial  Environment— Electric  Energy  and  the 

Sun's  Heat 

As  remarked  above,  in  the  change  from  the  lifeless  to  the 
life  world,  the  properties  of  the  chemical  life  elements  become 
known  as  the  functions  of  living  matter.  Stored  energy  becomes 
known  as  nutriment  or  food. 

The  earliest  function  of  living  matter  appears  to  have  been 
to  capture  and  transform  the  electric  energy  of  those  chemical 
elements  which  throughout  we  designate  as  the  "life  elements." 
This  function  appears  to  have  developed  only  in  the  presence 
of  heat  energy,  derived  either  from  the  earth  or  from  the  sun 
or  from  both;  this  is  the  first  example  in  the  life  process  of 
the  capture  and  utilization  of  energy  wherever  it  may  be  found. 
At  a  later  stage  of  evolution  life  captured  the  light  energy  of 
the  sun  through  the  agency  of  chloroph>ll,  the  green  coloring 
matter  of  plants.  In  the  final  stage  of  evolution  the  intellect 
of  man  is  capturing  and  controlling  physicochemical  energy  in 

many  of  its  forms. 

The  primal  dependence  of  the  electric  energy  of  life  on  the 
original  heat  energy  of  the  earth  or  on  solar  heat  is  demon- 
strated by  the  universal  behavior  of  the  most  primitive  organ- 
isms, because  when  the  temperature  of  protoplasm  is  lowered  to 
o°  C:  the  velocity  of  the  chemical  reactions  becomes  so  small 
that  in  most  cases  all  manifestations  of  life  are  suspended, 
that  is  Ufe  becomes  latent.  Some  bacteria  grow  at  or  very 
near  the  freezing-point  of  water  (o°  C.)  and  possibly  primordial 
bacteria-like  organisms  grew  below  that  point.     Even  now  the 


HEAT  AND  ELECTRIC  ENERGY 


49 


common  "hay  bacillus"  grows  at  6°  C    Rising  temperatures 
increase  the  velocity  of  the  biochemical  reactions  of  proto- 
plasm up  to  an  optimum  temperature,  beyond  which  they  are  in- 
creasingly injurious  and  finally  fatal  to  all  organisms.     In  hot 
springs  some  of  the  Cyanophyceae  (blue-green  alga?),  primitive 
plants  intermediate  in  evolution  between  bacteria  and  alga;, 
sustain  temperatures  as  high  as  63°  C.  and,  as  a  rule,  are  killed 
by  a  temperature  of  73°  C,  which  is  probably  the  coagulation 
point  of  their  proteins.     Setchell  found  bacteria  living  in  water 
of  hot  springs  at  89°  C.-     In  the  next  higher  order  of  the  Chlo- 
rophyceae  (green  algae)  the  temperature  fatal  to  Ufe  is  lower, 
being  43°  C.^     Very  much  higher  temperatures  are  endured  by 
the  spores  of  certain  bacilli  which  survive  until  temperatures 
of  from  105°  C.  to  120°  C.  are  reached.     There  appears  to  be 
no  known  limit  to  the  amount  of  dry  cold  which  they  can 

withstand.^ 

It  is  this  power  of  the  relatively  water-free  spores  to  resist 
heat  and  cold  which  has  suggested  to  Richter  (1865),  to  Kel- 
vin, and  to  Arrhenius  (1908)  that  living  germs  may  have  per- 
vaded space  and  may  have  reached  our  planet  either  in  com- 
pany with  meteorites  (Kelvin)^  or  driven  by  the  pressure  of 
light  (Arrhenius) .«  The  fact  that  so  far  as  we  know  life  on  the 
earth  has  only  originated  once  or  during  one  period,  and  not 
repeatedly,  does  not  appear  to  favor  these  hypotheses;  nor  is 
it  courageous  to  put  off  the  problem  of  life  origin  into  cosmic 

■  Jordan,  Edwin  O.,  1908,  pp.  67,  68.  '  Op-  cil.,  p.  68. 

=  Loeb,  Jacques,  1906,  p.  106.  . ,  ,    j 

<  Cultures  of  bacteria  have  even  been  exposed  to  the  temperature  of  liquid  hydrogen 
(about  —250°  C.)  without  destroying  their  vitality  or  sensibly  impairing  their  biologic 
qualities  This  temperature  is  far  below  that  at  which  any  chemical  reaction  is  known 
to  take  place,  and  is  only  about  23  degrees  above  the  absolute  zero  |K>int  at  which,  it  is 
believed,  molecular  movement  ceases.  On  the  other  hand,  when  bacteria  arc  frozen  in 
water  during  the  formation  of  natural  ice  the  death  rate  is  high.     Sec  Jordan,  Edwm  O., 

1908,  p.  69. 

'  Poulton,  Edward  B.,  1896,  p.  818. 

•  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  1915,  PP-  535,  536- 


so  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

space  instead  of  resolutely  seeking  it  within  the  forces  and 
elements  of  our  own  humble  planet. 

The  thermal  conditions  of  Uving  matter  point  to  the  prob- 
ability that  life  originated  at  a  time  when  portions  at  least 


Fig.  s-    The  Earliest  Phvla  of  Plant  and  Animal  Life. 
Chart  showing  the  theoretic  derivation  of  chordates  and  vertebrates  from  some  inverte- 
brate stok   and  of  the  invertebrates  from  some  of  the  protozoa     The  diagonal  Imes 

indtau  ^he  geologic  date  of  the  --'-'*«--/-"'--  :"i^'=  cTI,^,;^ tee  "„ 
The  earliest  well-known  invertebrate  fauna  is  in  the  Middle  Cambrian  tsee  pp. 
Ti8-,T/TndTigs    20-.7).     .\lthough  diatoms  are  among  the  simplest  known   liv- 

from  the  Cretaceous. 

of  the  earth's  surface  and  waters  had  temperatures  of  between 
89°  C.  and  6°  C;  and  also  to  the  possibility  of  the  origin  of 
life  before  the  atmospheric  vapors  admitted  a  regular  supply 
of  sunlight. 


THE  CAPTURE  OF  SUNLIGHT 


51 


\ 


Capture  of  the  Energy  of  Sunlight 
After  the  sun's  heat  living  matter  appears  to  have  captured 
the  sun's  light,  which  is  essential,  directly  or  indirectly,  to  all 
living  energy  higher  than  that  of  the  most  primitive  bacteria. 
The  discovery  by  Lavoisier  (i 743-1 794)  and  the  development 
(1804)  by  de  Saussure'  of  the  theory  of  photosynthesis,  namely, 
that  sunshine  combining  solar  heat  and  light  is  a  perpetual 
source  of  living  energy,  laid  the  foundations  of  biochemistry 
and  opened  the  way  for  the  establishment  of  the  law  of  the 
conservation  of  energy  within  the  living  organism. 

Thus  arose  the  first  conception  of  the  cycle  of  the  elements 
continually  passing  through  plants  and  animals  which  was  so 
grandly  formulated  by  Cuvier  in  1817:^  "La  vie  est  done  un 
tourbiUon  plus  ou  moins  rapide,  plus  ou  moins  complique, 
dont  la  direction  est  constante,  et  qui  entraine  toujours  des 
molecules  de  memes  sortes,  mais  ou  les  molecules  individuelles 
entrent  et  d'oii  elles  sortent  continuellement,  de  maniere  que 
Isi  forme  du  corps  vivant  lui  est  plus  essentielle  que  sa  matiere." 

Chemical  Composition  of  Chlorophyll' 


Carbon ' -^ '  •5'* 

Hydrogen ^H 

N.  .  .         S • Oo 
itrogen ^ 

Oxygen ^^t 

Phosphorus ^  '  ^ 

Magnesium ^'^"^ 

lOO.OO 


The  green  coloring  matter  of  plants  is  known  as  chloro- 
phyll; its  chemical  composition  according  to  Hoppe-Seyler's 

1  De  Saussure,  N.  T.,  1804. 

2  Cuvier,  Baron  Georges  L.  C.  F.  D.,  181 7,  p.  i3. 

3  Sachs,  Julius,  1882,  p.  758. 


52  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

analysis  is  given  here.     Potassium  is  essential  for  its  assimi- 
lating activity.     Iron  (often  accompanie.d  by  manganese),  al- 
though essential  to  the  production  of  chlorophyll,  is  not  con- 
tained in  it.     The  chlorophyll-bearing  leaves  of  the  plant  m 
the   presence   of   sunlight   separate   oxygen    atoms   from    the 
carbon  and  hydrogen  atoms  in  the  molecules  of  carbon  dioxide 
(CO2)  and  of  water  (H,0),  storing  up  the  energy  of  the  hydro- 
gen and  carbon  products  in  the  carbohydrate  substances  of  the 
plant,  an  energy  which  is  stored  by  deoxidation  (separation  of 
oxygen),  and  which  can  be  released  only  through  reoxidation 
(addition  of  oxygen).     Thus  the  celluloses,  sugars,  starches, 
and  other  similar  substances  deposit  their  kinetic  or  stored 
energy  in  the  tissues  of   the   plant  and   release   that '  energy 
through  the  addition  of  oxygen,  the  amount  of  oxygen  required 
being  the  same  as  that  needed  to  burn  these  substances  m 
the  air  to  the  same  degree;  in  brief,  through  a  combustion 
which  generates  heat.'     Thus  living  matter  utilizes  the  energy 
of  the  sun  to  draw  a  continuous  stream  of  electric  energy  from 
the  chemical  elements  in  the  earth,  the  water,  and  the  atmos- 
phere. 

This  was  the  first  step  in  the  interpretation  of  life  processes 
in  the  terms  of  physics  and  chemistry,  rather  than  in  terms 
of  a  peculiar  vitalism.     What  had  previously  been  regarded 
as  a  special  vital  force  in  the  life  of  plants  thus  proved  to  be 
an  adaptation  of  physicochemical  forces.     The  chemical  action 
of  chlorophyll  is  even  now  not  fully  understood,  but  it  is  known 
to  absorb  most  vigorously  the  solar  rays  between  B  and  C  of 
the  spectrum,^  and  these  rays  are  most  effective  in  the  assim- 
ilation of  energy  or  food  by  the  plant.     While  the  effect  of  the 
solar  rays  between  D  and  E  is  minimal,  those  beyond  F  are 
.  again  effective.^    In  heliotropic  movements  both  of  plants  and 


1 W.  J.  Gies. 


Locb,  Jacques,  1906,  p.  115. 


IONIZATION 


S3 


. 


animals  the  blue  rays  are  more  effective  than  the  red.'  Spores 
given  off  as  ciliated  cells  from  the  algae  seek  first  the  blue  rays. 
Since  the  food  supply  of  animals  is  primarily  derived  from 
chlorophyll-bearing  plants,  animals  are  less  directly  dependent 
on  the  solar  light  and  solar  heat,  while  the  chemical  life  of 
plants  fluctuates  throughout  the  day  with  the  variations  of 
light  and  temperature.  Thus  Richards^  finds  in  the  cacti  that  v 
the  breaking  down  of  the  acids  through  the  splitting  of  the 
acid  compounds  is  a  respiratory  process  caused  by  the  alternate 
oxidation  and  deoxidation  of  the  tissues  through  the  action  of/ 

the  sun. 

The  solar  energy  transformed  into  the  chemical  potential  I 
energy  of  the  compounds  of  carbon,  hydrogen,  and  oxygen  in 
the  plants  is  transmuted  by  the  animal  into  motion  and  heat 
and  then  dissipated.  Thus  in  the  life  cycle  we  observe  both 
the  conservation  and  the  degradation  of  energy,  corresponding 
with  the  first  and  second  laws  of  thermodynamics  developed 
in  physics  by  the  researches  of  Newton,  Helmholtz,  Phillips, 
Kelvin,  and  others.-'  The  remaining  life  processes  correspond^ 
in  many  ways  to  Newton's  third  law  of  motion. 

Action  and  Reaction  as  Adaptive  Properties  of  the  Life 

Elements 

The  adaptation  of  the  chemical  elements  to  life  processes 
is  due  to  their  incessant  action  and  reaction,  each  element 
having  its  peculiar  and  distinctive  forms  of  action  and  reaction, 
which  in  the  organism  are  transmuted  into  functions.  Such 
activity  of  the  life  elements  is  largely  connected  with  forms 
of  electric  energy  which  the  physicists  call  ionization,  while 
the  correlated  or    coordinated   interaction   of  various    groups 


'  op.  cil.,  i>.  1 27- 


Richards,  Herbert  M.,  1913,  PP-  34,  73-75- 


=  Henderson,  Lawrence  J.,  1913,  pp-  15-18- 


54  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

of  life  elements  is  largely  connected  with  processes  which  the 

chemists  term  catalysis. 

y  Ionization,  the  actions  and  reactions  of  all  the  elements  and 
electrolytic  compounds-according  to  the  hypothesis  of  Arrhe- 
nius,  first  put  forth  in  1887-is  primarily  due  to  electrolytic 
dissociation  whereby  the  molecules  of  all  acids  (e.  g.,  carbonic 
acid  H.CO3),  bases  {e.  g.,  sodium  hydroxide,  NaOH),  and  salts 
(e.  g',  sodium  chloride,  NaCl)  give  off  streams  of  the  electrically 
charged  particles  known  as  ions.     Ionization  is  dependent  on 
the  law  of  Nernst  that  the  greater  the  dielectric  capacity  of 
the  solvent  (e.  g.,  water)  the  more  rapid  will  be  the  dissociation 
of  the  substances  dissolved  in  it,  other  conditions  remaining 
Nthe  same. 
Ionization  of  the  Elements  thus  far  Discovered  in  Living  Organisms 


Mainly  or  Wholly  with  or  in  ^Negative  iuiis 


Mainly  or  Wholly  with  or  in  Positive  lons^ 


Non-metallic 


Carbon^  ie.  g.*  carbonates) 
Oxygen^  (e.  g.*  sulphates) 
Nitrogen^.a  (g.  g,4  nitrates) 
Phosphorus^  (e.  g.*  phosphates) 
Sulphur-  {e.  g.,*  sulphates) 
Chlorine  {e.  g.,*  chlorides) 


Silicon 

Iodine 

Bromine 

Fluorine 

Boron 

Arsenic^ 


Metallic 


Hydrogen^ 

Potassium 

Sodium 

Calcium 

Magnesium 

Manganese 


Iron' 

Copper 

Aluminum 

Barium 

Cobalt 

Lead 


Lithium 

Nickel 

Radium 

Strontium 

Zinc 


>  An  ion  is  an  atom  or  group  of  atoms  carrying  an  electric  charge.     The  positive  ions 
(cations)  of  the  metallic  elements  move  toward  the  cathode-  the  negat.ve  ions  (anions) 
oivpn  oft  bv  the  non-metallic  elements  move  toward  the  anode. 
^    ^Together  with  hydrogen  conspicuous  in  living  colloids  and  non-electrolytes-very 

""•3  ciccur:  STn  "  iX'ions.    Here  the  hydrogen  overbalances  the  nitrogen. 

:ScTirfTat^e:a.!tTi:urg  compounds  it  is  an  analogue  of  phosphorus 

nnfl  occurs  in  nemtive  ions  when  ionized.  . ,  ,     ,  .  u- 

» Pktet  has  obtained  results  indicating  that  liquid  and  solid  hydrogen  are  metallic. 
Hvdroeen  is  metallic  in  behavior,  though  non-metalhc  in  appearance.  ....      , 

''iron  in  iTving  compounds  is  chiefly  non-ionized,  colloidal.  Apparently  th^  is  ako 
true  of  copper,  aluminum,  barium,  cobalt,  lead,  nickel,  strontium,  and  zinc.  As  to  ra- 
dium,  however,  there  is  no  information  on  this  point. 

Thus,  ions  are  atoms  or   groups  of   atoms  carrying  electric 
charges  which  are  positive  when  given  off  from  metallic  ele- 


1 


\ 


IONIZATION 


55 


ments,  and  negative  when  given  off  from  non-metallic  elements. 
Electrolytic  molecules,  according  to  this  theory,  are  constantly 
dissociating  to  form  ions,  and  the  ions  are  as  constantly  recom- 
bining  to  form  molecules.  Since  the  salts  of  the  various  min- 
eral elements  are  constantly  being  decomposed  through  elec- 
trolytic ionization,  they  play  an  important  part  in  all  the  life 
phenomena;  and  since  similar  decomposition  is  induced  by 
currents  of  electricity,  indications  are  that  all  the  development 
of  Hving  energy  is  in  a  sense  electric. 

The  ionizing  electric  properties  of  the  life  elements  are  a 
matter  of  prime  importance.     We  observe  at  once  in  the  table 
above  that  all  the  great  structural  elements  which  make  up 
the  bulk  of  plant  and  animal  tissues  are  of  the  non-metallic 
group  with  negative  ions,  with  the  single  exception  of  hydro- 
gen which  has  positive  ions.     All  these  elements  are  of  low 
atomic  weight,  and  several  of  them  develop  a  great  amount 
of  heat  in  combustion,  hydrogen  and  carbon  leading  in  this 
function  of  the  release  of  energy,  which  invariably  takes  place 
in  the  presence  of  oxygen.     On  the  other  hand,  the  lesser  com- 
ponents of  living  compounds  are  the  metallic  elements  with 
positive  ions,  such  as  potassium,  sodium,  calcium,  and  mag- 
nesium, calcium  combining  with  carbon  or  with  phosphorus 
as  the  great  structural  or  skeletal  builder  in  animals.     There  is 
also  so  much  carbonaceous  protein  in  the  animal  skeleton  that 
calcium  in  animals  takes  the  place  of  carbon  in  plants  only  in 
the  sense  that  it  reduces  the  proportion  of  carbon  in  the  skele- 
ton: it  shares  the  honors  with  carbon. 

In  general  the  electric  action  and  reaction  of  the  non- 
metaUic  and  the  metallic  elements  dissolved  or  suspended  in 
water  are  now  believed  to  be  the  chief  phenomena  of  the  in- 
ternal functions  of  life,  for  these  functions  are  developed  always 
in  the  presence  of  oxygen  and  with  the  energy  either  of  the 


\ 


y 


56 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


/ 


heat  of  the  earth  or  of  the  sun,  or  of  both  the  heat  and  light 

of  the  sun. 

Finally,  we  observe  that  ionization  is  connected  with  the 
radioactive  elements,  of  which  thus  far  only  radium  has  been 
detected  in  the  organic  compounds,  although  the  others  may 

be  present. 

Phosphorescence  in  plants  and  animals  is  treated  by  Loeb' 
and  others  as  a  form  of  radiant  energy.  While  developed  in  a 
number  of  living  animals— including  the  typical  glowworms  in 
which  the  phenomenon  was  first  investigated  by  Faraday— the 
living  condition  is  not  essential  to  it  because  phosphorescence 
continues  after  death  and  may  be  produced  in  animals  by 
non-living  material.  Many  organisms  show  phosphorescence 
at  comparatively  low  temperatures,  yet  the  presence  of  free 
oxygen  appears  to  be  necessary. 

In  Rutherford's  experiments  on  radioactive  matter^  he  tells 
us  that  in  the  phosphorescence  caused  by  the  approach  of  an 
emanation  of  radium  to  zinc  sulphate  the  atoms  throw  off  the 
alpha  particles  to  the  number  of  five  billion  each  second,  with 
velocities  of  10,000  miles  a  second;  that  the  alpha  particles  in 
their  passage  through  air  or  other  medium  produce  from  the 
neutral  molecules  a  large  number  of  negatively  charged  ions, 
\^nd  that  this  ionization  is  readily  measurable. 

Interaction  or  Coordination  of  the  Properties  of  the 

Life  Elements 

The  actions  and  reactions  of  the  life  elements,  which  are 
mainly  contemporaneous,  direct,  and  immediate,  do  not  sufTice 
to  form  an  organism.  As  soon  as  the  grouping  of  chemical 
elements  reaches  the  stage  of  an  organism  inlcraction  also  be- 
comes essential,  for  the  chemical  activities  of  one  region  of  the 

« Loeb,  Jacques,  1906,  pp.  66-68.  "  Rutherford,  Sir  Ernest,  1915,  p.  "S- 


COORDINATION 


57 


organism  must  be  harmonized  with  those  of  all  other  regions; 
the  principle  of  interaction  may  apply  at  a  distance  and  the 
results  may  not  be  contemporaneous.     This  is  actually  inferred 
to  be  the  case  in  single-celled  organisms,  such  as  the  Amceba.' 
The  interacting  and  coordinating  form  of  lifeless  energy 
which  has  proved  to  be  of  the  utmost  importance  in  the  life 
processes  is  that  recognized  in  the  early  part  of  the  nineteenth 
century  and  denoted  by  the  term  catalysis,  first  apphed  by\ 
Berzelius  in  1835.     A  catalyzer  is  a  substance  which  modifies 
the   velocity   of   any  chemical   reaction   without   itself    being 
used  up  by  the  reaction.     Thus  chemical  reactions  may  be 
accelerated  or  retarded,  and  yet  the  catalyzer  lose  none  of 
its  energy.     In  a  few  cases  it  has  been  definitely  ascertamed 
that   the   catalytic   agent   does   itself   experience   a   series  of 
changes.     The   theory   is   that   catalytic   phenomena   depend 
upon  the  alternate  decomposition  and  recomposition,  or  the 
alternate  attachment  and  detachment  of  the  catalytic  agent. 
Discovered  as  a  property  in  the  inorganic  world,  catalysis 
has  proved  to  underlie  the  great  series  of  functions  in  the 
organic  world  which  may  be  comprised  in  the  physical  term 
interaction.     The  researches  of  Ehrlich  and  others  fully  justify 
Huxley's  prediction  of  188 1  that  through  therapeutics  it  would 
become  possible  "to  introduce  into  the  economy  a  molecular 
mechanism  which,  like  a  cunningly  contrived  torpedo,  shall 
fmd  its  way  to  some  particular  group  of  living  elements  and 
cause  an  explosion  among  them,  leaving  the  rest  untouched." 
In  fact,  the  interacting  agents  known  as  "enzymes"  are  such 
living  catalyzers,^  and  accelerate  or  retard  reactions  in  the 
body  by  forming  intermediary  unstable  compounds  which  are 
rapidly  decomposed,  leaving  the  catalyzer  {i.  e.,  enzyme)  free 
to  repeat  the  action.     Thus  a  small  quantity  of  an  enzyme 


1  Calkins,  Gary  N.,  191'),  I'P-  ^59.  ^^o. 


-  Loeb,  Jacques,  1906,  pp.  26,  28. 


58 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


Ncan  decompose  indefinite  quantities  of  a  compound.  The 
activity  of  enzymes  is  rather  in  the  nature  of  the  '' interaction'' 
of  our  theory  than  of  direct  action  and  reaction,  because  the 
results  are  produced  at  a  distance  and  the  energy  Hberated 
may  be  entirely  out  of  proportion  to  the  internal  energy  of  the 
catalyzer.  The  enzymes,  being  themselves  complex  organic 
compounds,  act  specifically  because  they  do  not  affect  alike  the 
different  organic  compounds  which  they  encounter  in  the  fluid 
circulation. 

Adaptation  in  the  Colloidal  State 

In  the  Ufeless  world  matter  occurred  both  in  the  crystal- 
loidal  and  colloidal  states.     It  is  in  the  latter  state  that  life 
originated.     It  is  a  state  peculiarly  favorable  to  action,  reac- 
tion, and  interaction,  or  the  free  interchange  of  physicochemi- 
cal  energies.     Each  organism  is  in  a  sense  a  container  full  of 
a  watery  solution  in  which  various  kinds  of  colloids  are  sus- 
pended.^    Such  a  suspension  involves  a  play  of  the  energies  of 
the  free  particles  of  matter  in  the  most  delicate  equilibrium, 
and  the  suspended  particles  exhibit  the  vibrating  movement 
attributed  to  the  impact  of  the  molecules.-     These  free  parti- 
cles are  of  greater  magnitude  than  the  individual  molecules;  in 
fact,  they  represent  molecules  and  multimolecules,  and  all  the 
known  properties  of  the  compounds  known  as  ''colloids''  can 
be  traced  to  feeble  molecular  affinities  between  the  molecules 
themselves,  causing  them  to  unite  and  to  separate  in  multi- 
molecules.     Among  the  existing  living  colloids  are  certain  car- 
bohydrates, like  starch  or  glycogen,  proteins  (compounds  of 
carbon,  hydrogen,  oxygen,  and  nitrogen  with  sulphur  or  phos- 
phorus), and  the  higher  fats.     The  colloids  of  protoplasm  are 
dependent  for  their  stability  on  the  constancy  of  acidity  and 


1  Bechhold,  Heinrich,  191 2. 


2  Smith,  Alexander,  1914,  p.  305- 


FUNCTIONS  OF  LIFE  ELEMENTS 


59 


alkalinity,  which  is  more  or  less  regulated  by  the  presence  of 

bicarbonates.' 

Electrical  charges  in  the  colloids'  are  demonstrated  by  cur- 
rents of  electricity  sent  through  a  colloidal  solution,  and  are 
interpreted  by  Freundlich  as  due  to  electrolytic  dissociation  of 
the  colloidal  particles,  alkaline  colloids  being  positively  charged,^ 
while  acid  colloids  are  negatively  charged.  The  concentration 
of  hydrogen  and  hydroxyl  ions  in  the  ocean  and  in  the  organ- 
ism is  automatically  regulated  by  carbonic  acid.' 

Among  the  colloidal  substances  in  living  organisms  the  so- 
called  enzymes  are  very  important,  since  they  are  responsible 
for  many  of  the  processes  in  the  organism.  Possibly  enzymes 
are  not  typical  colloids  and  perhaps,  in  pure  form,  they  may 
not  be  classified  as  such;  but  if  they  are  not  colloids  they  cer- 
tainly behave  like  colloids.^ 

Cosmic  Properties  and  Life  Functions  of  the  Chief 

Chemical  Life  Elements 

r 

Of  the  total  of  eighty-two  or  more  chemical  elements  thus 
far  discovered  at  least  twenty-nine  are  known  to  occur  in  liv- 
ing organisms  either  invariably,  frequently,  or  rarely,  as  shown 
in  Table  11  of  the  Life  Elements.  Whether  essential,  fre- 
quent or  of  rare  occurrence,  each  one  of  these  elements-as 
described  below-has  its  single  or  multiple  services  to  render 

to  the  organism. 

Hydrogen,  the  life  element  of  least  atomic  weight,  is  always 
near  the  surface  of  the  typical  hot  stars.  Rutherford^  tells  us 
that  while  the  hydrogen  atom  is  the  lightest  known,  its  nega- 
tively charged  electrons  are  only  about  1/1800  of  the  mass  of 


1  Henderson,  Lawrence  J.,  iQiS^PP-  i57-i6o. 
3  Henderson,  Lawrence  J.,  i9i3»  P-  257- 
6  Rutherford,  Sir  Ernest,  1915,  P-  ^^S- 


Loeb,  Jacques,  1906,  pp.  34,  35' 
<  Hedin,  Sven  G.,  1915,  PP-  164, 173- 


6o 


THE   ORIGIN  AND   EVOLUTION  OF   LIFE 


the  hydrogen  atom:  they  are  Hberated  from  metals  on  which 
ultra-violet  light  falls,  and  can  be  released  from  atoms  of  mat- 


FiG.  6.    Hydrogen  Vapor  in  the  Solar  Atmosphere 
Hydrogen,  which  far  exceeds  anv  other  element  in  the  amount  of  heat  it  yields  upon 
oxidation  (see  Table  H,  p.  67)  and  ranks  among  the  four  most  important  of  the  chemical 
life  elements,  is  also  invariably  present  at  the  surface  of  all  typical  hot  stars,  includ- 
ing the  sun.     The  large  masses  of  hydrogen  vapor  known  as  "solar  prominences 
which  burst  forth  from  every  part  of  the  sun,  are  here  shown  as  photographed  during  a 
total  eclipse.     The  upper  figure  presents  a  detail  from  the  lower,  greatly  enlarged 
From  the  Mount  Wilson  Observatory. 

ter  by  a  variety  of  agencies.     Hydrogen  is  present  in  all  acids 
and   in   most   organic   compounds.     It   also   has   the   highest 


FUNCTIONS  OF  LIFE  ELEMENTS 


61 


power  of  combustion.'  Its  ions  are  very  important  factors  in 
animal  respiration  and  in  gastric  digestion.'^  It  is  very  actiVe 
in  dissociating  or  separating  oxygen  from  various  compounds, 
and  through  its  affinity  for  oxygen  forms  water  (H2O),  the 
principal  constituent  of  protoplasm. 


Fig  7     Hydrogen  Flocculi  Surrounding  a  Group  of  Sun-Spots. 
The  vortex  structure  is  clearly  shown.    After  Hale.     From  the  Mount  Wilson 

Observatory. 

Oxygen,  like  hydrogen,  has  an  attractive  power  which  brings 
into  the  organism  other  elements  useful  in  its  various  functions. 
It  makes  up  two-thirds  of  all  animal  tissue,  as  it  makes  up 
one-half  of  the  earth's  crust.  Besides  these  attractive  and  syn- 
thetic functions,  its  great  service  is  as  an  oxidizer  in  the  release 
of  energy;  it  is  thus  always  circulating  in  the  tissues.  Through 
this  it  is  involved,  in  all  heat  production  and  in  all  mechanical 
work,  and  affects  cell  division  and  growth.' 

•  Henderson,  Lawrence  J.,  I9i3>  PP-  "^'  239,  24S- 

«  W.  J.  Gies.  '  Lo^'*'  Jacques,  1906,  p.  16. 


62 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


FUNCTIONS  OF  LIFE  ELEMENTS 


63 


Nitrogen  comes  next  in  importance  to  hydrogen  and  oxygen 
as  structural  material  and  when  combined  with  carbon  and 
sulphiir  gives  the  plant  and  animal  world  one  of  the  chief 
organic   food   constituents,   protein.     It   was   present   on   the 
primordial  earth,  not  only  in  the  atmosphere  but  also  in  the 
gases  and  waters  emitted  by  volcanoes.     Combined  with  hy- 
drogen it  forms  various  radicles  of  a  basic  character  {e.  g.,  NH2 
in  amino-acids,  NH4  in  ammonium  compounds) ;  combined  with 
oxygen  it  yields  acidic  radicles,  such  as  NO3  in  nitrates.     It 
combines  with  carbon  in  —  C  =  N  radicles  and  in  =  C  —  NH2 
and  =^  C  =  NH  forms,  the  latter  being  particularly  important 
in  protoplasmic  chemistry.^     This  life  element  forms  the  basis 
of  all  explosives,  it  also  confers  the  necessary  instability  upon 
the  molecules  of  protoplasm  because  it  is  loath  to  combine 
with  and  easy  to  dissociate  from  most  other  elements.     Thus 
we  find  nitrogen  playing  an  important  part  in  the  physiology 
of  the  most  primitive  organisms  known,  the  nitrifying  bacteria. 
Carbon  also  exists  at  or  near  the  surface  of  cooling  stars 
which  are  becoming  red.^     It  unites  vigorously  with  oxygen, 
tearing  it  away  from  neighboring  elements,  while  its  tendency 
to  unite  with  hydrogen  is  less  marked.     At  lower  heats  the 
carbon  compounds  are  remarkably  stable,  but  they  are  by  no 
means  able  to  resist  great  heats;  thus  Barrell*  observes  that  a 
chemist  would  immediately  put  his  finger  on  the  element  car- 
bon as  that  which  is  needed  to  endow  organic  substance  with 
complexity  of  form  and  function,  and  its  selection  in  the  origin 
'  of  plant  life  was  by  no  means  fortuitous.     Including  the  arti- 
ficial products,  the  known  carbon  compounds  exceed  100,000, 
while  there  are  thousands  of  compounds  of  C,  H,  and  O,  and 
hundreds  of  C  and  H.^     Carbon  is  so  dominant  in  living  mat- 

1  Henderson,  Lawrence  J.,  1913,  P-  241.  ^  W.  J.  Gies. 

3  Henderson,  Lawrence  J.,  1913,  P-  55-  *  Joseph  Barrell,  letter  of  March  20,  1916. 

5  Henderson,  Lawrence  J.,  19131  PP-  ^93.  i94- 


ter  that  biochemistry  is  very  largely  the  chemistry  of  carbon 
compounds;  and  it  is  interesting  to  observe  that  in  the  evolu- 
tion of  life  each  of  these  biological  compounds  must  have  arisen 
suddenly  as  a  saltation  or  mutation,  there  being  no  continuity 
between  one  chemical  compound  and  another. 

Phosphorus  is  essential  in  the  nucleus  of  the  cell,^  being  a 
large  constituent  of  the  intranuclear  germ-plasm  known  as 
chromatin,  which  is  the  seat  of  heredity.  It  enters  largely 
into  the  structure  of  nerves  and  brain  and  also,  in  the  form 
of  phosphates  of  calcium  and  magnesium,  serves  an  entirely 
diverse  function  as  building  material  for  the  skeletons  of 
animals.  Phosphates  are  important  factors  in  the  maintenance 
of  normal  uniformity  of  reaction  in  the  blood. 

Sulphur,  uniting  with  nitrogen,  oxygen,  hydrogen,  and  car- 
bon, is  an  essential  constituent  of  the  proteins  of  plants  and 
animals.2  jt  jg  especially  conspicuous  in  the  epidermal  protein 
known  as  keratin,  which  by  its  insolubility  mechanically  pro- 
tects the  underlying  tissues.^  Sulphur  is  also  contained  in 
one  of  the  physiologically  important  substances  of  bile.^  Sul- 
phates are  important  factors  m  the  protective  destruction,  in 
the  Hver,  of  poisons  of  bacterial  origin  normally  produced  in 
and  absorbed  from  the  large  intestine. 

Potassium  is  able  to  separate  hydrogen  from  its  union  with 
oxygen  in  water,  and  is  the  most  active  of  the  metals,  biologi- 
cally considered,  in  its  positive  ionization.^  Through  stimula- 
tion and  inhibition  potassium  salts  play  an  important  part  in 
the  regulation  of  life  phenomena,  and  they  are  essential  to  the 
living  tissues  of  plants  and  animals,  fresh-water  and  marine 
plants  in  particular  storing  up  large  quantities  in  their  tissues.^ 


1  op.  cit.,  p.  241. 

3  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  1915,  p.  434- 

*  Cajsium  is  more  electropositive. — F.  W.  Clarke. 

«  Loeb,  Jacques,  1906,  p.  94. 


^Op.  cit.,  p.  242. 
*  W.  J.  Gies. 


64  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

Potassium  is  of  service  to  life  in  building  up  complex  com- 
pounds from  which  the  potassium  cannot  be  dissociated  as  a 
free   ion;    it   is   thus   one   of   the   building   stones   of    livmg 

matter.* 

Magnesium  is  fourth  in  order  of  activity  among  the  metallic 
elements.  It  is  essential  to  chlorophyll,  the  green  colormg 
matter  of  plants,  which  in  the  presence  of  sunshine  is  able 


Fig.  8.    The  Sun,  Showing  Scn-Spots  and  Calcium  Vapor. 

ralcium   a  life  element  essential  to  all  plants  and  animals,  and  especially  abundant  in 

leTo'nes  L  Sth  of  vertebrates,  is  also  a  constituent  of  the  solar  atmosphere,  as 

hown  bv  thesltwo  photographs  of  the  sun,  both  displaying  the  same  v.ew  and    he 

mroup  oTsun-st^ts.    The  one  at  the  left,  made  by  calcium  rays  alone  with  the 

!^rtrn  helioeraoh  '  ^ows  in  addition  the  clouds  of  calcmm  vapor  which  are  not 

Stt  ^pttograph  at  the  right.     From  the  Mount  Wilson  Observatory. 

.  An  instrument  devised  bv  Protesor  George  E.  Hale  for  taking  photographs  of  the  sun  by  the  hght  of  a 

single  ray  of  the  spectrum  (calcium,  hydrogen,  etc.). 

to  dissociate  oxygen  from  the  carbon  of  carbon  dioxide  and 
from  the  hydrogen  of  water.  It  is  also  found  in  the  skeletons 
of  many  invertebrates  and  in  the  coralline  algae,  and  is  an  im- 
portant factor  in  inhibiting  or  restraining  many  biochemical 

processes.  ' 

Calcium  is  third  in  order  of  activity  among  the  metaUic 
elements.     According  to  Loeb^  it  plays  an  important  part  m 

^  op.  cU.,  p.  72.  «0^^7.,  i9o6,p.94. 


FUNCTIONS  OF  LIFE  ELEMENTS 


65 


the  life  phenomena  through  stimulation  (irritabiUty)  and  in- 
hibition. It  unites  with  carbon  as  carbonate  of  lime  and  is 
contained  in  many  of  those  animal  skeletons  which,  through 
deposition,  make  up  an  important  part  of  the  earth's  crust. 


Fig.  9.    Chemical  Life  Elements  in  the  Sun. 

Three  regions  of  the  solar  spectrum  with  lines  showing  the  presence  of  such  essential 
life  elements  as  carbon,  nitrogen,  calcium,  iron,  magnesium,  sodmm,  and  hydrogen. 
From  the  Mount  Wilson  Observatory. 

In  invertebrates  the  carbonates,  except  in  certain  brachiopods, 
are  far  more  important  as  skeletal  material  than  the  phosphates: 
the  limestones  form  only  about  five  per  cent  of  the  sedimen- 
taries.     Shales  and  sandstones  are  far  more  abundant. 

Iron  is  essential  for  the  production  of  chlorophyll,^  though, 
unlike  magnesium,  it  is  not  contained  in  it.  It  is  present  as 
well  in  all  protoplasm,  while  in  the  higher  animals  it  serves,  in 

1  Sachs,  Julius,  1882,  p.  699. 


1 


66 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


the  form  of  oxyhemoglobin,  as  a  carrier  of  oxygen  from  the 
lungs  to  the  tissues.^ 

Sodium  is  less  important  in  the  nutrition  of  plant  tissues, 
but  serves  an  essential  function  in  all  animal  life  in  relation  to 
movement  through  muscular  contraction.-  Its  salts,  like  those 
of  calcium,  play  an  important  part  in  the  regulation  of  life  phe- 
nomena through  stimulation  and  inhibition.^ 

Iodine,  with  its  negative  ionization,  becomes  useful  through 
its  capacity  to  unite  with  hydrogen  in  the  functioning  of  the 
brown  algae  and  in  many  other  marine  organisms.  It  is  also 
an  organic  constituent  in  the  thyroid  gland  of  the  vertebrates.* 
The  iodine  content  of  crinoids — stalked  echinoderms — varies 
widely  in  organisms  gathered  from  different  parts  of  the  ocean 
according  to  the  temperature  and  the  iodine  content  of  the 
sea-water.  Iodine  and  bromine  are  important  constituents  of 
the  organic  axes  of  gorgonias. 

Chlorine,  like  iodine,  a  non-metallic  element  with  negative 
ions,  is  abundant  in  marine  algae  and  present  in  many  other 
plants,  while  in  animals  it  is  present  in  both  blood  and  lymph. 
In  union  with  hydrogen  as  hydrochloric  acid  it  serves  a  very 
important  function  in  the  gastric  digestion  of  proteins.  ^ 

Barium,  rarely  present  in  plants,  has  been  used  in  animal 
experimentation  by  Loeb,  who  has  shown  that  its  salts  induce 
muscular  peristalsis  and  accelerate  the  secretory  action  of  the 
kidneys.^ 

Copper  ranks  first  in  electric  conductivity.  In  the  inverte- 
brates, in  the  form  of  hemocyanine,  it  acts  as  an  oxygen  carrier 
in  the  fluid  circulation  to  the  tissues.^  It  is  always  present  in 
certain  molluscs,  such  as  the  oyster,  and  also  in  the  plumage 


^  Henderson,  Lawrence  J.,  1913,  p.  241. 

3  Op.  cit.,  pp.  94,  95. 

^Op.  cit.,  p.  242. 

'Henderson,  Lawrence  J.,  1913,  p.  241. 


*  Loeb,  Jacques,  1906,  p.  79. 

*  Henderson,  Lawrence  J.,  1913,  p.  242. 

*  Loeb,  Jacques,  1906,  p.  93. 


TABLE  II.    ADAPTIVE   FUNCTIONS  OF  THE   LIFE   ELEMENTS   IN  PLANTS  AND   ANIMALS 


Atomic 
Weight 


i.cx>8 
12.005 
16.00 
14.01 

32.06 
39.10 

24.32 

40.07 
55-84 


23.00 
35  46 
28.3 


ELEMENTS  INVARIABLY  PRESENT  IN  LIVING  ORGANISMS 


Heat  Combustion 
Per  Gram 


34 .  702  cal.  (Ha) 
8.08      " 


0.143 

5-747 

2.22 
1-745 

6.077 

3  284 
I  353 


3-293 


0.254 


{( 


(( 


(( 


Element 


Hydrogen 

Carbon 

Oxygen 

Nitrogen 

Phosphorus 

Sulphur 
Potassium 

Magnesium 

Calcium 
Iron 


PSodium 
PChlorine 
?  Silicon 


Symbol 


H 
C 
O 

N 
P 

S 
K 

Mg 

Ca 
Fe 


Na 

CI 

Si 


Plants 


Animals 


Hydrogen,  carbon,  oxygen,  and  nitrogen — "H,  C,  O,  N" — are  essential  and  of  chief  rank  in  all  life  processes;   forming, 
with  sulphur,  practically  all  plant  and  animal  proteins  and,  with  phosphorus,  forming  the  nucleoproteins. 


In  nucleoproteins  and  phospholipins. 

In  "most  proteins,  o.i-'5.o  per  cent. 

Abundant  in  marine  plants,  esp.  "kelps"  (larger  Phaophy- 
cea) ;  activity  of  chlorophyll  depends  on  it. 

Present  in  large  quantities  in  Corallinacea  (a  family  of  cal- 
cified refl  algae). 

Present  in  large  quantities  in  certain  algae  (chiefly  marine). 

Essential  in  the  formation  of  protoplasm;  present  in  chlo- 
rophyll. 

Believed   essential   to  all  plants,  but  not  demonstrated; 

found  in  marine  plants,  esp.  Phaophyccct. 
Present  in  many  plants;   believed  by  some  to  be  essential; 

abundant  in  marine  algae,  esp.  in  the  Phceophycece. 
Found  in  all  plants;  present  in  large  quantities  in  the  Dia- 

tomacece,  both  fresh-water  and  marine;  in  form  of  "silica" 

constitutes  0.5-7.0  per  cent  of  the  ash  of  ordinary  marine 

alga\ 


In  nucleoproteins  and  phospholipins;  in  some  brachiopods; 

in  blood;  and  in  vertebrate  bone  and  teeth. 
In  most  proteins,  0.1-5.0  per  cent. 
In  blood,  muscle,  etc. 

Present  in  echinoderms  and  alcyonarians;  present  in  all 
parts  of  vertebrates,  esp.  in  bones. 

In  all  parts  of  vertebrates;   abundant  in  bones  and  teeth. 

Essential  in  the  formation  of  protoplasm,  and  in  the 
higher  animals;  essential  in  hemoglobin  as  an  oxygen- 
carrier. 

Present  in  all  animals;  abundant  in  blood  and  lymph. 

Present  in  all  animals;    abundant  in  blood  and  lymph; 

present  in  the  gastric  juice. 
Present  in  radiolarians  and  siliceous  sponges;    also  in  all 

the  higher  animals. 


ELEMENTS  FREQUENTLY  PRESENT  IN  LIVING  ORGANISMS 


12(3.92 

54-03 
79.92 

19.0 


o.  1766  cal. 


Iodine 

Manganese 
Bromine 

Fluorine 


Mn 
Br 

F 


In  marine  plants,  esp.   the  "brown  algae,"    Phceophycea ; 

in  Laminaria  and  Fitcus;  also  in  some  Gorgonias. 
In  some  plants. 
In  marine  plants,  esp.  the  "brown  algae,"  Phceophycco! ;  m 

some  Gorgonias. 
In  a  few  plants. 


Essential  in  the  higher  animals  (thyroid). 

In  most  animals  in  very  slight  proportions. 
In  some  animals  in  very  slight  proportions. 

In   some   animals — constituent   of  bones   and   teeth;     in 
shells  of  mollusks  and  in  vertebrate  bones. 


ELEMENTS  RARELY  PRESENT  IN  LIVING  ORGANISMS 


27 

I 

74 

96 

137 

37 

II 

0 

58 

97 

63 

57 

207 

20 

6 

94 

.S8 

68 

226 

0 

87-63 

^5-37 


1 .463  cal. 
0.952    " 


0.58- 


0.243 


T.497 
1 .  291 


(( 


t( 


(( 


(( 


Aluminum  ' 

Al 

Arsenic  ^ 

As 

Barium  ' 

Ba 

Boron 

B 

Cobalt » 

Co 

Copper  ' 

Cu 

Lead' 

Pb 

Lithium 

Li 

Nickel  ' 

Ni 

Radium  ' 

Ra 

Strontium  ' 

Sr 

Zinc  ' 

Zn 

In  a  few  plants. 

In  a  few  plants. 
In  some  plants. 
In  a  few  plants. 
In  a  few  plants. 


In  some  plants. 
In  a  few  plants. 
In  some  plants. 

Ill  a  ft'w  plants. 
In  a  k'W  [)iants. 


In  a  few  animals. 
In  some  animals. 


Traces  in  some  corals;   essential  in  some  lower  animals  as 

ox>  gen-carrier. 
Traces  in  some  corals. 


In  some  animals. 

In  a  few  animals;  traces  in  some  corals. 


The  exceedingly  rare  occurrence  of  cerium,  chromium,  didymium,  lanthanum,  molybdenum,  and  vanadium  is  in  all  probability  merely  adventitious. 
'  Commonly  regarded  as  {xjisons  when  {)resent  in  m'nural  (ionic)  forms,  even  in  small  proj>orlions. 


PRIMARY   STAGES   OF   TJFE 


67 


of  a  ])ir(l,  the  Turaco.  Although  among  the  rare  life  elements 
it  ranks  first  in  toxic  action  upon  fungi,  algie,  and  in  general 
upon  all  plants,  yet  it  is  occasionally  found  in  the  tissues  of 
trees  growing  in  copper-ore  regions.^ 

In  general  most  of  the  metallic  compounds  and  several  of 
the  non-metallic  compounds  are  toxic  or  destructive  to  life 
when  present  in  large  quantities.  All  the  mineral  elements  of 
high  atomic  weight  are  toxic  in  comparatively  minute  propor- 
tions, while  the  essential  life  elements  of  low  atomic  w^eight 
are  toxic  only  in  comparatively  large  proportions.  Toxicity 
depends  largely  upon  the  liberation  of  ions,  and  non-ionized 
and  non-ionizable  organic  compounds — such  as  hemoglobin 
containing  non-ionizable  iron — are  wholly  non-toxic. 

Pure    Speculation   as  to   the   Primary  Physicochemical 

Stages  of  Life 

The  mode  of  the  origin  of  life  is  a  matter  of  pure  specula- 
tion, in  which  we  have  as  yet  little  observation  or  uniformitarian 
reasoning  to  guide  us,  for  all  the  experiments  of  Biitschli  and 
others  to  imitate  the  original  life  process  have  proved  fruitless. 
We  shall,  however,  from  our  knowledge  of  bacteria  (see  Chap. 
Ill)  put  forward  five  hypotheses  in  regard  to  it,  considering  \ 
the  life  process  as  probably  a  gradual  one,  marked  by  short  leaps 
or  accessions  of  energy,  and  not  as  a  sudden  one. 

First:  We  amy  advance  the  hypothesis  that  an  early  step 
in  the  organization  of  living  matter  was  the  assemblage  one  by 
one  of  several  of  the  ten  elements  now  essential  to  life,  namely, 
hydrogen,  oxygen,  nitrogen,  carbon,  phosphorus,  sulphur,  po- 
tassium, calcium,  magnesium,  and  iron  (also  perhaps  silicon), 
which  are  present  in  all  living  organisms,  with  the  exception 
of  some  of  the  most  primitive  forms  of  bacteria  which  may 

*  M.  A.  Howe,  letter  of  February  24,  1916. 


*ai^«  fcg;:.jjgg*«:».s 


68 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


lack  magnesium,  iron,  and  silica.  Of  these  the  four  most  im- 
portant elements  were  obtained  from  their  previous  combina- 
tion in  water  (H2O),  from  the  nitrogen  compounds  of  volcanic 
emanations  or  from  the  atmosphere^  consisting  largely  of 
nitrogen,  and  from  atmospheric  carbon  dioxide  (CO2).  The 
remaining  six  elements,  phosphorus,  sulphur,  potassium,  cal- 
cium, magnesium,  and  iron,  came  from  the  earth. 

Second :  Whether  there  was  a  sudden  or  a  more  or  less  serial 
grouping  of  these  elements,  one  by  one,  we  are  led  to  a  second 
hypothesis  that  fhey  were  gradually  bound  by  a  new  form  of 
mutual  attraction  whereby  the  actions  and  reactions  of  a  group 
of  life  elements  established  a  new  form  of  unity  in  the  cosmos, 
an  organic  unity,  an  individual  or  organism  quite  distinct  from 
the  larger  and  smaller  aggregations  of  inorganic  matter  pre- 
viously held  or  brought  together  by  the  forces  of  gravity. 
Some  such  stage  of  mutual  attraction  may  have  been  ancestral 
to  the  cell,  the  primordial  unity  and  individuality  of  which  we 

shall  describe  later. 

Third :  This  leads  to  the  hypothesis  that  this  grouping  oc- 
curred in  the  gelatinous  state  described  as  '^colloidal''  by 
Graham.'^  Since  all  living  cells  are  colloidal,  it  appears  prob- 
able that  this  grouping  of  the  '4ife  elements'^  took  place  in  a 
state  of  colloidal  suspension,  for  it  is  in  this  state  that  the  life 
elements  best  display  their  incessant  action,  reaction,  and 
.interaction.  Bechhold^  observes  that  ^^  Whatever  the  arrange- 
ment of  matter  in  living  organisms  in  other  worlds  may  be,  it 
must  be  of  colloidal  nature.     What  other  condition  except  the 

1  Ammonia  is  also  formed  by  electrical  action  in  the  atmosphere  and  unites  with  the 
nitric  oxides  to  form  ammonium  nitrate  or  nitrite;  these  compounds  fall  to  earth  m  ram. 
p  W  Clarke. 

2  Over  fifty  years  ago  Thomas  Graham  introduced  the  term  "colloid"  (L.  colla,  glue) 
to  denote  non-crystalloid  indifTusible  substances,  like  gelatine,  a  typical  colloid,  as  dis- 
tinguished from  diffusible  crystalloids.  Proteins  belong  to  that  class  of  coUoids  which, 
once  coagulated,  cannot,  as  a  rule,  be  redissolved  in  water. 

3  Bechhold,  Heinrich,  191 2,  p.  194. 


NEW  ORGANIC  COMPOUNDS 


69 


♦» 


colloidal  could  develop  such  changeable  and  plastic  forms,  and 
yet  be  able,  if  necessary,  to  preserve  these  forms  unaltered?'' 

Fourth:  As  a  fourth  hypothesis  relating  to  the  origin  of 
organisms,  we  may  advocate  the  idea  that  the  evolution  and  ^ 
specialization  of  various  "  chemical  messengers ''  known  as 
catalyzers  (including  enzymes  or  ''unformed  ferments'')  has 
proceeded  step  by  step  with  the  evolution  of  plant  and  animal 
functions.  In  the  evolution  from  the  single-celled  to  the  many- 
celled  forms  of  life  and  the  multiplication  of  these  cells  into 
hundreds  of  millions,  into  billions,  and  into  trillions,  as  in  the 
larger  plants  and  animals,  biochemical  coordination  and  cor- 
relation became  increasingly  essential.  This  cooperation  was 
also  an  application  of  energy  new  to  the  cosmos. 

Fifth:  With  this  assemblage,  mutual  attraction,  colloidal 
condition,  and .  chemical  coordination,  a  fifth  hypothesis  is 
that  there  arose  the  rudiments  of  competition  and  Natural 
Selection  which  tested  all  the  actions,  reactions,  and  inter- 
actions of  two  competing  individuals.  Was  there  any  stage  in 
this  grouping,  assemblage,  and  organization  of  Ufe  forms,  how- 
ever remote  or  rudimentary,  when  the  law  of  natural  selection 
did  not  operate  between  different  unit  aggregations  of  matter  ? 
Probably  not,  because  each  of  the  chemical  life  elements  possesses 
its  peculiar  properties  which  in  living  compounds  best  serve  cer- 
tain functions. 

Evolution  of  New  Organic  Compounds 

Special  actions  and  reactions  appear  to  be  characteristic  of 
each  of  the  life  elements,  issuing  in  new  compounds. 

The  central  idea  in  our  five  hypotheses  (see  p.  67)  of  suc- 
cessive physicochemical  stages  is  that  in  the  origin  and  early 
evolution  of  the  life  organism  there  was  a  gradual  attraction 
and  grouping  of  the  ten  chief  life  elements,  followed  by  the 


70  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

grouping  of  the  nineteen  or  more  chemical  elements  which  were 
subsequently  added.  The  creation  of  new  chemical  compounds 
may  have  been  analogous  to  the  successive  addition  of  new 
characters  and  functions,  such  as  we  now  observe  through 
paleontology  in  the  origin  and  development  of  the  higher 
plants  and  animals,  resembling  a  series  of  inventions  and  dis- 
coveries by  the  organism. 

Conceivable  steps  in  the  process  were  as  follows:     From 
earth,  air,  and  water  there  may  have  been  an  early  grouping 
of  oxygen,  nitrogen,  hydrogen,  and  carbon,  such  as  we  witness 
in  the  lowliest  bacterial  stages  of  life.     Even  those  lifeless  com- 
pounds which  contain  neither  hydrogen,  carbon,  nor  oxygen, 
make  up  but  a  very  small  percentage  of  the  substance  of  known 
bodies.     The   compounds   of   carbon,   hydrogen,   and   oxygen 
(C,  H,  O)'  constitute  a  unique  ensemble  of  fitness  among  all 
the  possible  chemical  substances  for  the  exchange  of  matter 
and  energy  within  the  life  organism  and  between  it  and  its 
environment.     As  the  higher  forms  of  life  are  constituted  to- 
day, water  and  the  carbon  dioxide  of  the  atmosphere  are  the 
chief  materials  of  the  complicated  life  compounds,  and  also 
the  common  end  products  of  the  materials  yielding  energy  to 
the  body.     Proteins  are  made  from  materials  containing  nitro- 
gen in  addition. 

Thus  may  have  arisen  the  utilization  of  the  binary  com- 
pounds of  carbon  and  oxygen  (CO.),  and  of  hydrogen  and 
oxygen  (H2O),  to  the  attractive  power  of  which  Henderson^ 
has  especially  drawn  our  attention.  It  is  this  attractive  power 
of  oxygen  or  of  hydrogen  or  of  both  elements  combined  which 
is  now  bringing,  and  in  the  past  may  have  brought  into  the 
life  organism  other  elements  useful  to  it  in  its  various  func- 

'Henderson,  Lawrence  J.,  1913,  pp.  7".  '94,  195.  -^o?.  23i>  ^i^- 
■Op.  cU.,   pp.  239,  240. 


INTERACTIONS 


71 


1 


l 


' 


tions.  Thus  in  the  origin  of  life  hydrogen  and  oxygen,  ele- 
ments unrivalled  in  chemical  activity,  functioned  as  ^^attrac- 
tive'' agents  to  enable  the  life  organism  to  draw  in  other  chem- 
ical elements  to  serve  new  purposes  and  functions. 

Through  such  attraction  or  other  means  the  incorporation 
of  the  active  metals— potassium,  sodiurh,  calcium,  magnesium, 
iron,  manganese,  and  copper— into  the  substance  of  living 
organisms  may  have  occurred  in  the  order  of  their  utility  in 
capturing  energy  from  the  environment  and  storing  it  withm 
the  organism.  For  example,  an  immense  period  of  geologic 
time  may  have  elapsed  before  the  addition  of  magnesium  and 
iron  to  certain  hydrocarbons  enabled  the  plant  to  draw  upon 
the  energy  of  solar  light.  This  marked  the  appearance  of 
chlorophyll  in  the  earliest  algal  stage  of  plant  life. 

Evolution  of  Interactions 

The  organism  as  a  whole  is  made  a  harmonious  unit 
through  interaction.  Its  actions  and  reactions  must  be  regu- 
lated, balanced,  coordinated,  correlated,  protected  from  foreign 
invasion,  accelerated,  retarded.  This  harmony  seems  in  large 
part  to  be  due  to  the  principle  that  every  action  and  reaction 
sends  off  as  a  by-product  a  ''chemical  messenger"  which  sooner 
or  later  produces  an  interaction  at  some  more  or  less  distant 

point. 

The  regulating  and  balancing  of  actions  and  reactions  within 
the  organism  was  provided  for  by  the  presence  in  the  fluid  cir- 
culation of  outside  chemical  agents,"  for  many  of  the  primordial 
actions  and  reactions  arc  known  to  give  rise  to  chemical  by- 
products which  circulate  throughout  the  Ufe  organism.  Among 
such  regulating  and  balancing  influences  we  observe  that  ex- 
erted by  the  phosphates  upon  the  acidifying  tendency  of  carbon 


72 


THE  ORIGIN  AND   EVOLUTION  OF   LIFE 


dioxide;^  in  respiration  carbon  dioxide  raises  the  hydrogen  con- 
centration of  the  blood;  the  phosphates  restrain  this  tendency, 
while  the  breathing  apparatus,  in  response  to  stimuli  from  the 
respiratory  centres  irritated  by  the  hydrogen,  throws  out  the 
excess  of  this  element. 

Thus  there  evolved  step  by  step  the  function  of  coordinating 
and  correlating  the  activities  of  various  parts  of  the  life  organ- 
ism remote  from  each  other  by  means  of  chemical  messen- 
gers adapted  to  effect  not  only  a  general  interaction  between 
general  parts,  but  also  special  interactions  between  special 
parts;  for  it  is  now  known  that,  as  Huxley  prophesied  (see 
p.  57),  certain  chemical  messengers  do  reach  particular  groups 
of  living  elements  and  leave  others  entirely  untouched.  For 
example,  the  enzyme  developed  in  the  yeast  ferment  produces 
a  different  result  in  each  one  of  a  series  of  closely  related  carbo- 
hydrates.- 

These  chemical  messengers  are  doubtless  highly  diversified; 
they  are  now  known  to  exist  in  at  least  three  or  four  forms, 
as  follows: 

First:  The  simplest  forms  of  such  chemical  messengers  are 
those  which  originate  as  by-products  of  single  chemical  reactions. 
For  example,  the  carbon  dioxide  (CO2)  liberated  in  the  cell  by 
the  reactions  of  respiration  acts  at  a  distance  on  other  portions 
of  the  cell  and  of  the  organism.  Thus  every  cell  of  the  body 
furnishes  in  the  carbon  dioxide  which  it  eUminates  a  chemical 
messenger,'^  since  under  normal  conditions  the  carbon  dioxide 
of  the  blood  is  one  of  the  chief  regulators  of  the  respiratory 
centre,  influencing  this  centre  by  virtue  of  its  acidic  properties. 

Second:  Of  prime  importance  among  the  various  '^chemical 
messengers'^  are  the  organic  catalyzers^  known  as  enzymes ^  the 

^  W.  J.  Gies.  2  Moore,  F.  J.,  1915   p.  170;  Loeb,  Jacques,  1906,  pp.  21,  22. 

'  Abel,  John  J.,  1915,  p.  168.  *  Loeb,  Jacques,  1906,  pp.  8,  28. 


CHEMICAL   MESSENGERS 


73 


action  of  which  has  already  been  described  (see  p.  s?)-     They 
appear  to  be  present  in  all  cells,  and  in  most  cases  the  ac- 
tivity of  the  cell  itself  depends  upon  them.^     These  enzymes 
are  very  probably  of  a  protein  nature  and  are  readily  destroyed 
by  heat  in  the  presence  of  water.     The  active  agents  of  the 
external  secretions  when  present  are  always  of  the  nature  of  a 
ferment  or  enzyme.     Driesch^-  has  suggested  that  the  nucleus 
of  the  cell  is  a  storehouse  of  these  ferments  which  pass  out 
into  the  protoplasm  tissues  and  there  set  up  specific  activities.^ 
Third:  Antigens.,  antibodies  including  the  agents  of  immunity.^ 
The  active  and  inactive  protein  compounds  termed  antigens  in- 
clude certain  known  proteins  and  possibly  a  few  other  com- 
pounds of  kindred  nature.    Among  the  active  protein  compounds 
are  certain  enzymes,  bacterial  poisons,  snake  venoms,  spider 
poisons,  and  some  vegetable  poisons;  antigens  of  this  class  are 
all  powerfully  active  and  possess  properties  which  suggest  that 
they  may  eventually  be  classed  as  enzymes.     On  the  invasion 
of  an  organism  by  any  foreign  protein  of  this  class  in  any 
region   except  the  interior  of   the  alimentary  canal  it  would 
seem  that  certain  chemical  messengers  called  antibodies  arise 
which  are  especially  fitted  to  protect  the  tissues  of  the  body 
against  such  invasion;  these  antibodies  are  true  agents  of  im- 
munity and  serve  to  increase  the  resistance  of  the  organism  to 
any  future  attack  of  the  invading  antigen;  it  is  to  this  forma- 
tion of  neutralizing  antibodies,  known  as  antitoxins,  that  the 
curative  powers  for  such  infections  as  diphtheria  and  tetanus 

are  due.  . 

There  are  also  antigens  of  another  kind,  consisting  of  mo^- 
tvve  protein  compounds,  which,  when  they  invade  an  organism, 
induce  the  formation  of  antibodies  acting  in  an  entirely  dif- 

^  Schafer,  Sir  Edward  A.,  1916,  pp.  4,  5-  =  Wilson,  Edmund  B.,  1906,  p.  427. 

3  Zinsser,  Hans,  1915,  PP-  223-226,  247,  248. 


74 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


ferent  manner  from  the  antitoxins.  While  antibodies  of  this 
kind  tend  to  assimilate  or  remove  the  invading  antigen,  they 
do  not  confer  immunity  against  a  future  invasion:  on  the  con- 
trary, they  render  the  organism  increasingly  susceptible.  Ex- 
periments on  animals  show  that,  while  the  first  injection  of 
such  inactive  proteins  may  be  entirely  harmless,  subsequent 
injections  may  result  in  severe  injury  or  even  death. 

It  is,  therefore,  evident  that  the  invasion  of  an  organism 
either  by  a  powerfully  active  or  by  an  inactive  antigen  causes 
changes  of  a  physicochemical  nature  which  appear  to  originate 
in  the  body  cell  itself,  resulting  in  the  formation  of  chemical 
messengers  known  as  antibodies  which  appear  in  the  circulat- 
ing blood. 

Fourth:  Of  vital  importance  to  the  life  organism  are  those 
chemical  messengers  known  as  internal  secretions,  due  for  the 
most  part  to  the  so-called  endocrine  (Gr.  evhov,  within,  and 
Kplvo),  to  separate)  organs  or  ductless  glands,  which  liberate 
some  specific  substance  within  their  cells  that  passes  directly 
into  the  blood  stream  and  has  a  stimulating  or  inhibiting  effect 
upon  other  organs.  To  certain  of  these  stimulating  internal 
messengers  Starling  applied  the  term  ''hormone"  (Gr.  6pfid(o, 
to  awaken,  to  stir  up).  Recently  Schafer,^  in  reviewing  all 
the  organs  of  internal  secretion,  has  proposed  the  opposite 
term  ''ghalone"  (Gr.  x^^^^y  to  make  slack)  for  those  messen- 
gers which  depress,  retard,  or  inhibit  the  activity  of  distant 
parts  of  the  body.  The  interactions  between  different  parts 
of  the  organism  produced  by  these  chemical  messengers  depend 
upon  a  simpler  chemical  constitution  than  that  of  the  enzymes,- 
as  hormones  and  chalones,  for  the  most  part,  are  not  rendered 
inactive,  even  by  prolonged  boiling. 

We  may  suppose  that  in  the  course  of  evolution  certain 

*  Schafer,  Sir  Edward  A.,  1916,  p.  5.  *  Loc.  cit. 


CHEMICAL  MESSENGERS 


75 


f 


special  cells  and,  finally,  special  groups  of  cells  gave  rise  to 
the  glands,  and  none  of  the  discoveries  we  have  hitherto  de- 
scribed throws  greater  illumination  on  the  whole  process  of 
building  up  an  elaborate  life  organism  than  those  connected 
with  the  products  of  internal  secretion.  Among  the  special 
glands  of  internal  secretion  known  in  man  are  the  thyroids, 
parathyroids,  thymus,  suprarenals,  pituitary  body,  and  pineal 
gland,  rudiments  of  which  doubtless  occur  in  the  very  oldest 
vertebrates  and  even  among  their  invertebrate  ancestors;  al- 
though their  functions  have  been  discovered  chiefly  through 
experiment  upon  the  lower  mammals  and  man. 

Of  the  chemical  messengers  produced  by  these  glands  some 
affect  the  growth  of  the  entire  organism,  while  others  affect 
only  certain  parts  of  the  organism;  some  arrest  growth  entirely, 
others  stimulate  growth  at  certain  points  only,  and  others  again 
entirely  change  the  proportions  of  certain  parts  of  the  body. 
Thus  an  injury  to  the  pituitary  body,  which  lies  beneath  the 
vertebrate  brain,  results  in  stunted  stature,  marked  adiposity, 
and  delayed  or  imperfect  sexual  development;  on  the  other 
hand,  a  diseased  condition  of  the  pituitary  body,  rousing  it 
to  excessive  function,  is  followed  by  a  great  increase  in  the 
general  size  of  the  head,  as  well  as  by  a  complete  change  in 
the  proportions  of  the  face  from  broad  to  long  and  narrow, 
and  an  abnormal  growth  of  the  long  limb-bones,  while  at  the 
same  time  the  proportions  of  the  hands  are  changed  from  nor- 
mal to  the  short  and  broad  condition  known  as  brachydactyly.^ 
In  other  words,  the  regulation  and  balance  resulting  in  the 
normal  size  and  proportions  of  certain  parts  of  the  skeleton 
are  dependent  upon  chemical  messengers  coming  from  these^ 
glands. 

1  Schafer,   Sir  Edward  A.,    1916,   pp.  107,   108,    no.     Gushing,    Harvey,   1911,  pp. 
253»  256. 


76 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


It  has  also  been  discovered  that  the  source  of  such  internal 
secretions  is  not  confined  to  the  ductless  glands,  but  that  cer- 
tain duct-glands,  sxiCh  as  the  ovaries,  testes,  and  pancreas, 
serve  a  double  function,  for  they  secrete  not  only  through 
their  ducts,  but  they  also  produce  an  internal  secretion 
which  enters  the  circulation  of  the  blood.  It  is,  of  course,  a 
fact  known  from  remote  antiquity  that  removal  of  the  sex 


Fig.  io.    Hand  Form  Determined  by  Heredity  (A)  and  by  Abnormal  Internal 

Secretions  {B,  C). 

A.  Hereditary  brachydactyly  (partial)  attributed  to  congenital  causes.    After  Drink  water. 

B.  Acquired  brachydactyly.     This  abnormally  broad  and  stumpy  hand  shows  one  of  the 

results  of  abnormally  excessive  secretions  of  the  pituitary  gland.     After  Gushing. 

C.  Acquired  dolichodactyly.     This  slender  hand  with  tapering  fingers  shows  one  of  the 

results  of  abnormally  insufficient  secretions  of  the  pituitary  gland.    After  Gushing. 

glands  from  a  young  animal  of  either  sex  not  only  inhibits  the 
development  of  all  the  so-called  secondary  sexual  characters, 
but  favors  the  development  of  characters  of  the  opposite  sex. 
During  the  last  and  present  centuries  it  has  been  discovered 
that  all  these  inhibited  characters  may  be  restored  by  success- 
fully transplanting  or  grafting  into  some  part  of  the  body  the 
ovary  or  testicle,  either  from  the  same  or  another  individual, 
thus  proving  that  in  both  sexes  the  secondary  sexual  characters 


CHEMICAL   MESSENGERS 


77 


are  dependent  upon  some  internal  secretion  from  the  ovaries 
and  testes  and  not  upon  the  normal  production  of  the  male 
and  female  germ-cells,  or  ova  and  spermatozoa. 

The  classic  demonstration  of  this  internal  messenger  sys-  \ 
tem  is  that  made  experimentally  by  Berthold  in  fowls.  In 
1849  he  transplanted  the  testicles  of  young  cocks  which  after- 
ward developed  the  masculine  voice,  comb,  sexual  desire,  and 
love  of  combat,  thus  anticipating  the  theories  of  Brown- 
Sequard,  who  committed  himself  to  the  view  that  a  gland, 
ductless  or  not,  sends  into  the  circulation  substances  essential 
to  the  normal  growth  and  maintenance  of  many  if  not  all  parts  ^ 
of  the  bodv. 

With  the  discovery  that  the  regulating  and  balancing  func- 
tions, as  well  as  the  accelerating  or  retarding  of  the  activities 
of  certain  characters  of  organisms,  are  phenomena  of  physico- 
chemical  action,  reaction,  and  interaction  in  individual  devel- 
opment, we  obtain  a  distant  glimpse  of  the  possible  causes  of 
the  balance,  development,  or  degeneration  of  certain  parts  of 
organisms  through  successive  generations,  and  conceivably  of 
the  long-sought  means  of  interaction  between  the  actions  and 
reactions  of  individual  development  (body-protoplasm  and 
body-chromatin)  and  of  the  germ-cells  in  race  development 
(heredity-chromatin) . 

In  fact,  a  heredity  hypothesis  was  proposed  by  Cunning- 
ham^ in  1906  based  upon  Berthold's  discovery  that  the  connec- 
tion between  the  germ-cells  and  the  secondary  sexual  organs  of 
the  body  was  really  of  a  chemical  rather  than  of  a  nervous 
nature  as  had  previously  been  supposed.  To  paraphrase  Gun-  >. 
ningham's  hypothesis  in  modern  terms,  since  hormones  and 
chalones  issuing  as  internal  secretions  from  the  groups  of  germ- 
cells  (ovaries  and  testes)  determine  the  development  of  many 

*  Cunningham,  J.  T.,  1908,  pp.  372-428. 


78 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


other  organs,  it  is  possible  that  hormones  and  chalones  arising 
from  the  various  cellular  activities  of  the  body  itself  may  act 
upon  the  physicochemical  elements  in  the  germ-cells  which 
correspond  potentially  to  the  tissues  from  which  these  hor- 
mones and  chalones  are  derived.  Cunningham  was  a  strong 
believer  in  the  Lamarckian  explanation  (see  p.  xiii)  of  evolu- 
tion, and  his  heredity  hypothesis  was  designed  to  suggest  a 
means  by  which  the  modifications  of  the  body  due  to  environ- 
mental and  developmental  conditions  could  so  modify  the 
corresponding  tissues  and  physicochemical  constitution  of  the 
chromatin  in  the  germ-cells  as  to  become  hereditary  and  re- 
W  appear  in  subsequent  generations. 


\^ 


Physicochemical  Differentiation 

As  the  result  of  recent  investigations  of  cancer,  Loeb^  comes 
to  the  following  conclusions: 

'*  We  must  assume  that  every  individual  of  a  certain  species 
differs  in  a  definite  chemical  way  from  every  other  of  that 
species,  and  that  in  its  chemical  constitution  an  animal  of  one 
species  differs  still  more  from  an  animal  of  another.  Every 
cell  of  the  body  has  a  chemical  character  in  common  with  ev- 
ery other  cell  of  that  body  and  also  in  common  with  the  body 
fluids;  and  this  particular  chemical  group  differs  from  that  of 
every  other  individual  of  the  species  and  to  a  still  greater  de- 
gree from  that  of  any  individual  of  another  group  or  species. 
Thus  it  happens  that  cells  belonging  to  the  same  organism  are 
adapted  to  all  the  other  cells  of  that  organism  and  also  to  the 
bodv  fluids.  .  .  . 

*^It  has  been  possible  to  demonstrate  by  experimental 
methods  that  there  are  fine  chemical  differences  not  only  be- 
tween different  species  and  between  different  individuals  of 

*  Loeb,  Leo,  1916,  pp.  209-226. 


PHYSICOCHEMICAL  DIFFERENTIATION 


79 


the  same  species,  but  also  between  different  sets  of  families 
which  constitute  a  strain,  for  certain  chemical  characters  dif- 
ferentiate them  from  other  strains  of  the  same  species.  It 
has  been  shown,  for  instance,  that  white  mice  bred  in  Europe 
differ  chemically  from  white  mice  bred  in  America,  although 
the  appearance  of  both  strains  may  be  identical.'' 

The  investigations  of  Reichert  and  Brown  (cited  in  Chapter 
VIII,  p.  247)  give  an  insight  into  the  almost  inconceivable 
physicochemical  complexity  of  a  single  element  of  the  blood, 
namely,  the  oxyhemoglobin  crystals. 


4 


EVOLUTION  OF  BACTERIA 


8i 


CHAPTER  III 

ENERGY  EVOLUTION  OF  BACTERIA,  ALG/E, 

AND  PLANTS 

Energy  and  form.  Primary  stages  of  biochemical  evolution  in  bacteria.  Evo- 
lution of  protoplasm  and  chromatin,  the  two  structural  components  of  the 
living  world.  Chlorophyll  and  the  energy  of  sunlight.  Evolution  of  the 
alga?.  Some  physicochemical  contrasts  between  plant  and  animal  evo- 
lution. 

We  shall  now  trace  some  of  the  physicochemical  principles 
of  action,  reaction,  and  interaction  as  they  actually  appear  in 
operation  in  some  of  the  simpler  forms  of  life,  beginning  with 
the  bacteria.  In  the  bacterial  organisms  the  capture,  storage, 
release,  and  interaction  of  energy  are  what  is  best  known  and 
apparently  most  important,  while  their  form  is  less  knovvTi  and 
apparently  less  important. 

Primary  Stages  of  Biochemical  Evolution  in  Bacteria 

A  bacterialess  earth  and  a  bacterialess  ocean  would  soon 
be  uninhabitable  either  for  plants  or  animals;  conversely,  it  is 
probable  that  bacteria-like  organisms  prepared  both  the  earth 
and  the  ocean  for  the  further  evolution  of  plants  and  animals, 
and  that  life  passed  through  a  very  long  bacterial  stage. 
/  In  the  origin  of  life  bacteria  appear  to  lie  half-way  be- 
tween our  hypothetical  chemical  precellular  stages  (pp.  67-71) 
and  the  chemistry  and  definite  cell  structure  of  the  lowliest 
plants,  or  algae.  Owing  to  their  minute  size  or  actual  invisibil- 
ity, bacteria  are  classified  less  by  their  shape  than  by  their 
chemical  actions,  reactions,  and  interactions,  the  analysis  of 

which  is  one  of  the  triumphs  of  modern  research. 

80 


The  size  of  bacteria  is  in  inverse  ratio  to  their  importance 
in  the  primordial  and  present  history  of  the  earth.  The  largest 
known  are  slightly  above  1/20  of  a  millimetre  in  length  and 
1/200  of  a  millimetre  in  width.  ^  The  smaller  forms  range 
from  I  /2000  of  a  millimetre  to  organisms  on  the  very  limit  of 
microscopic  vision,  i  /5000  of  a  millimetre  in  size,  and  to  the 
bacteria  beyond  the  limits  of  microscopic  vision,  the  existence 
of  which  is  inferred  in  certain  diseases.  The  chemical  consti- 
tution of  these  microscopic  and  ultramicroscopic  forms  is 
doubtless  highly  complex.  The  number  of  these  organisms  is 
inconceivable.  In  the  daily  excretion  of  a  normal  adult  human 
being  it  is  estimated  that  there  are  from  128,000,000,000  to 
33,000,000,000,000  bacteria,  which  would  weigh  approximately 
5  5/10  grams  when  dried,  and  that  the  nitrogen  in  this  dried 
mass  would  be  about  0.6  gram,  constituting  nearly  one-half 
the  total  intestinal  nitrogen.^ 

The  discoverv  of  the  chemical  life  of  the  lowliest  bacteria 
marks  an  advance  toward  the  solution  of  the  problem  of  the 
origin  of  life  as  important  as  that  attending  the  long-prior  dis- 
covery of  the  chemical  action  of  chlorophyll  in  plants. 

In  their  power  of  finding  energy  or  food  in  a  lifeless  world 
the  bacteria  known  as  prototrophic^  or  "primitive  feeders,''  are 
not  only  the  simplest  known  organisms,  but  it  is  probable 
that  they  represent  the  survival  of  a  primordial  stage  of  life 
chemistry.  These  bacteria  derive  both  their  energy  and  their*\\ 
nutrition  directly  from  inorganic  chemical  compounds:  such 
types  were  thus  capable  of  living  and  flourishing  on  the  lifeless     . 

earth  even  before  the  advent  of  continuous  sunshine  and  long/ 

) 

*  The  influenza  bacillus,  5/10  X  2/10  of  a  micron  (i/iooo  mm.)  in  size,  and  the  germ 
of  infantile  paralysis,  measuring  2/  10  of  a  micron,  are  on  the  limit  of  microscopic  vision. 
Beyond  these  are  the  ultramicroscopic  bacteria,  beyond  the  range  of  vision,  some  of 
which  can  pass  through  a  porcelain  filter.     See  Jordan,  Edwin  0.,  1908,  pp.  52,  53. 

2  Kendall,  A.  I.,  1915,  p.  209. 


/ 


82 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


EVOLUTION  OF  BACTERIA 


83 


before  the  first  chlorophyllic  stage  (Algae)  of  the  evolution  of 
plant  life.  Among  such  bacteria,  possibly  surviving  from 
I  Archaeozoic  time,  is  one  of  these  ''primitive  feeders/'  namely, 
the  Nitroso  monas  of  Europe.^  For  combustion  it  takes  in 
oxygen  directly  through  the  intermediate  action  of  iron,  phos- 
phorus,  or  manganese,  each  of  the  single  cells  being  a  powerful 
little  chemical  laboratory  which  contains  oxidizing  catalyzers, 
the  activity  of  which  is  accelerated  by  the  presence  of  iron  and 
of  manganese.  Still  in  the  primordial  stage,  Nitroso  monas 
lives  on  ammonium  sulphate,  taking  its  energy  (food)  from 
the  nitrogen  of  ammonium  and  forming  nitrites.  Living  sym- 
biotically  with  it  is  Nitrobader,  which  takes  its  energy  (food) 
from  the  nitrites  formed  by  Nitroso  monas,  oxidizing  them 
into  nitrates.  Thus  these  two  species  illustrate  in  its  simplest 
form  our  law  of  the  interaction  of  an  organism  (Nitrobacter)  with 
its  life  environment  {Nitroso  monas)  r 

These  organisms  are  wide-spread:  Nitroso  monas  is  found 
in  Europe,  Asia,  and  xAfrica,  while  Nitrobacter  appears  to  be 
almost  universally  distributed. 

These  "primitive  feeders''  are  classed  among  the  nitrifying 
bacteria  because  they  take  up  the  nitrogen  of  ammonia  com- 
pounds. Heraeus  and  Huppe  (1887)  were  the  first  to  observe 
these  nitrifiers  in  action  in  the  soils  and  to  prove  that  pre- 
chlorophyllic  organisms  were  capable  of  development,  with 
ammonium  and  carbon  dioxide  as  their  only  sources  of  energy. 
Nine  chemical  ''life  elements"  are  involved  in  the  life  reac- 
tions of  these  organisms,  namely,  sodium,  potassium,  phos- 
/  phorus,  magnesium,  sulphur,  calcium,  chlorine,  nitrogen,  and 
carbon.  This  discovery  was  confirmed  by  Winogradsky  (1890, 
1895),  who  showed  that  the  above  two  symbiotic  groups  ex- 
isted;  one  the  nitrite  formers,  Nitroso  monas,  and  the  other  the 

^  Fischer,  Alfred,  1900,  pp.  51,  104.  ^  Jordan,  Edwin  O.,  1908,  pp.  492-497. 


' 


m 


nitrate  formers,  Nitrobacter,  These  bacteria  are  not  only  in- 
dependent of  life  compounds,  but  even  small  traces  of  organic 
carbon  and  nitrogen  compounds  are  injurious  to  them.  Later 
Nathanson  (1902)  and  Beyjerinck  (1904)  showed  that  certain 
sulphur  bacteria  possess  similar  powers  of  converting  ferrous  to^ 
ferric  oxide,  and  H2S  to  SO2. 

Such  bacterial  organisms  may  have  flourished  on  the  lifeless 
earth  and  chemically  prepared  both  the  earth  and  the  waters 
for  the  lowly  forms  of  plant  life.  The  relation  of  the  nitrifying 
bacteria  to  the  decomposition  of  rocks  is  well  summarized  by 
Clarke  in  the  following  passage:^  "Even  forms  of  life  so  low 
as  the  bacteria  seem  to  exert  a  definite  influence  in  the  decom- 
position  of  rocks.  A.  Mlintz  has  found  the  decayed  rocks  of 
Alpine  summits,  where  no  other  fife  exists,  swarming  with  the 
nitrifying  ferment.  The  limestones  and  micaceous  schists  of 
the  Pic  du  Midi,  in  the  Pyrenees,  and  the  decayed  calcareous 
schists  of  the  Faulhorn,  in  the  Bernese  Oberland,  offer  good 
examples  of  this  kind.  The  organisms  draw  their  nourishment 
from  the  nitrogen  compounds  brought  down  in  snow  and  rain; 
they  convert  the  ammonia  into  nitric  acid,  and  that  in  turn 
corrodes  the  calcareous  portions  of  the  'rocks.  A.  Stiitzer  and 
R.  Hartleb  have  observed  a  similar  decomposition  of  cement 
by  nitrifying  bacteria.  The  effects  thus  produced  at  any  one 
point  may  be  small,  but  in  the  aggregate  they  may  become 
appreciable.  J.  C.  Branner,  how^ever,  has  cast  doubts  upon 
the  validity  of  Muntz's  argument,  and  further  investigation 
of  the  subject  seems  to  be  necessary.'* 

It  is  noteworthy  that  it  is  the  nitrogen  derived  from  waters 
and  soils,  rather  than  from  the  atmosphere,  which  plays  the 
chief  part  in  the  life  of  these  organisms;  in  a  sense  they  repre- 
sent an  early  carbon  stage  of  chemical  evolution,  since  carbon 

1  Clarke,  F.  W.,  1916,  p.  485- 


84 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


/ 


is  not  their  prime  constituent,  also  adaptation  to  an  earth-and- 
water  environment  rather  than  to  an  atmospheric  one. 

In  our  portrayal  of  the  chemistry  of  the  lifeless  earth  it  is 
shown  how  the  chief  life  elements  essential  for  the  energy  and 
nutrition  of  the  nitrifying  bacteria,  namely,  sodium,  potassium, 
calcium,  and  magnesium,  with  potassium  nitrite  and  ammo- 
nium salts  as  a  source  of  nitrogen,  may  have  accumulated  in 
the  waters,  pools,  and  soils.  These  bacteria  were  at  once  the 
soil-forming  and  the  soil-nourishing  agents  of  the  primal  earth; 
they  throve  in  the  presence  of  en^ergy-liberating  compounds  of 
extremely  primitive  character.  It  is  important  to  note  that 
water  and  air  are  essential  to  vigorous  ammonium  reactions, 

\  whether  at  or  near  the  surface.  In  arid  regions  at  the  present 
time  the  ammonifying  bacteria  do  not  exist  on  the  dry  surface 
rocks,  but  act  vigorously  in  the  soils,  not  only  at  the  surface, 
but  also  in  the  lower  layers  at  depths  of  from  six  to  ten  feet, 
where  moisture  is  constant  and  the  porous  soil  well  aerated,^ 
thus  giving  rise  to  a  nitrogen-nourished  substratum,  which 
explains  the  deep  rooting  of  desert-dwelling  plants. 

y  A  second  point  of  great  significance  is  that  these  nitrifying 
organisms  are  heat-loving  and  light-avoiding;  they  are  dependent 
on  the  heat  of  the  earth  or  of  the  sun,  for,  like  all  other  bac- 
teria, they  carry  on  their  activities  best  in  the  absence  of  sun- 
shine, direct  sunlight  being  generally  fatal.  The  sterilizing 
effect  of  sunlight  is  due  partly  to  the  coagulation  of  the  bac- 
terial colloids  by  the  rays  of  ultra-violet  light.  The  sensitive- 
ness of  bacteria  to  sunlight  cannot,  however,  be  viewed  as 
evidence  against  their  geologic  antiquity,  because  their  undif- 
ferentiated structure  and  their  ability  to  live  on  inorganic 
foodstuffs  even  without  the  aid  of  sunshine  seem  to  favor  the 
idea  that  they  represent  a  very  primitive  form  of  life.- 


1' 


EVOLUTION  OF  BACTERIA 


85 


The  great  geologic  antiquity  even  of  certain  lower  forms 
of  bacteria  which  feed  on  nitrogen  is  proved  by  the  discovery, 
announced  by  Walcott^  in  1915,  of  a  species  of  pre-Palaeozoic 


B 


C 


,-^'      ♦ 


***V'*'l|(lJt  _ 


^Lipman,  Charles  B.,  1912,  pp.  7,  8,  16,  17,  20. 


2 1.  J.  Kligler. 


DBF 

Fig.  II.    Fossil  and  Living  Bacteria  Compared. 
Extremely  ancient  fossil  bacteria  (^1)  compared  with  similar    types  of  living  bacteria 

A.  Fossil  bacteria  from  the  pre-Cambrian  Newland  limestone  (Algonkian),  after  Walcott. 

B.  Existing  nitrifying  bacteria  found  in  soils — the  arrow  indicates  a  chain  series  similar 

to  that  of  Walcott's  fossil  bacteria. 
C  A  more  complex  type  of  nitrifying  bacteria  found  in  soils. 

D.  Nitrogen-fixing  bacteria  from  the  root  nodules  of  legumes.     Note  the  granular  struc- 

ture of  the  supposed  "chromatin." 

E.  Denitrifying  bacteria  found  in  soil  and  water. 

F.  Bacteria  stained  to  bring  out  the  chromatin  granules  or  "nuclei"  in  the  centre  of 

each  rod-like  bacterial  cell. 

fossil  bacteria  attributed  to  ''Micrococcus,''  but  probably 
related  rather  to  the  existing  Nitroso  coccus,  which  derives  its 
nitrogen  from  ammonium  salts. 

These  fossil  bacteria  were  found  in  a  section  of  a  chlorophyll- 

*  Walcott,  Charles  D.,  1915,  p.  256. 


{' 


86 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


Ml 


bearing  algal  plant  from  the  Newland  limestone  of  the  Algon- 
kian  of  Montana,  the  age  of  which  is  estimated  to  be  about 
33,000,000  years.  They  point  to  a  very  long  antecedent  stage 
of  bacterial  evolution.  In  this  section  (Fig.  11,  A),  at  the 
points  indicated  by  the  arrows,  there  is  a  little  chain  of  cells 
closely  similar  to  those  in  the  existing  species  of  Azotobacter,  an 
organism  that  fixes  atmospheric  nitrogen  and  converts  it  into 
a  form  utilizable  by  the  plant.  The  Algonkian  form  is  related 
to  the  other  nitrifiers,  Nitroso  coccus,  Nitroso  monas,  and  to 
Nitrobacter  which  lives  on  simple  salts  with  carbon  dioxide 
(CO2)  as  a  source  of  carbon. 

The  gradual  evolution  of  a  cellular  structure  in  these  organ- 
isms can  be  partly  traced  despite  their  excessively  minute  size. 
The  cell  structure  of  the  Algonkian  and  of  the  recent  Nitroso 
coccus  bacteria  (Fig.  11,  A,  B)  is  very  primitive  and  uniform  in 
appearance,  the  protoplasm  being  naked  or  unprotected;  this 
primitive  structure  is  also  seen  in  C,  another  type  of  nitrogen- 
fixer  of  the  soil,  which  is  chemically  more  complex  because  it 
can  obtain    its   nitrogen  either  from   the   inorganic   nitrogen 
compounds  or  from  the  organic  nitrogen  compounds  (amino- 
acids),  which  are  fatal  to  the  Xitroso  monas  and  the  Nitro- 
bacter forms.     The  arrow  points  to  a  group  of  cells  similar  in 
appearance  to  those  in  B.     A  higher  stage  of  granular  structure 
appears  in  D,  a  nitrogen-fixer  from  the  root  nodules  of  legumes, 
which  like  B  and  C  lives  on  inorganic  chemical  compounds, 
but  draws  upon  the  atmosphere  for  nitrogen  and  upon  sugar 
for  its  carbon;  we  observe  an  uneven  granular  structure  in  this 
cell.     This  may  be  an  illustration  of  an  early  type  of  parasitic 
adaptation.     The  next  type  of  bacterium  (£)  is  a  denitrifier, 
which  derives  its  oxygen  from  the  nitrates,  reducing  them  to 
nitrites  and  free  nitrogen  and  ammonia.     A  further  stage  of 
structural  and  chemical  evolution  is  seen  {F)  in  four  elongated 


EVOLUTION  OF   BACTERIA 


87 


t 


'  I 


i 


bacteria,  each  showing  a  rod-like  but  cellular  form  with  a 
deeply  staining  chromatin  or  nuclear  mass;  the  arrows  point 
to  cells  showing  these  chromatin  granules.  This  organism  is 
chemically  more  complex  in  that  it  can  secrete  a  powerful 
tryptic-like  enzyme  which  enables  it  to  utilize  complex  poly- 
pep  tids  and  proteins  (casein).  Also  it  is  an  obligatory  aerobic 
type,  being  unable  to  function  in  the  absence  of  free  oxygen. 

It  was  only  after  the  chlorophyllic,  carbon-storing  trueV 
plants  had  evolved  that  the  second  great  group  of  parasitic 
nitrifying  bacteria  arose  to  develop  the  power  of  capturing  and 
storing  the  nitrogen  of  the  atmosphere  through  life  association  or 
symbiosis  with  plants,  also  of  deriving  their  carbon,  not  from 
inorganic  compounds,  but  from  the  carbohydrates  of  plants. 
Such  users  of  atmospheric  nitrogen  and  of  plant  carbon  include 
three  general  types:  B.  radicicola,  associated  with  the  root 
formation  of  legumes  (compare  D,  Fig.  11),  Clostridium  (anaer- 
obic, i.  e.,  independent  of  free  oxygen),  and  Azotobacter  (aerobic^ 
i.  e.,  requiring  free  oxygen).^ 

It  seems  that  the  early  course  of  bacterial  evolution  was  in 
the  line  of  developing  a  variety  of  complex  molecules  for  per- 
forming a  number  of  metaboUc  functions,  and  that  the  visible 
cell  differentiation  came  later.'-  Step  by  step  the  chemical 
evolution  and  addition  of  increasingly  complex  actions,  reac- 
tions, and  interactions  appear  to  correspond  broadly  with  the 
structural  evolution  of  the  bacterial  organism  in  its  approach 
to  the  condition  of  a  typical  cell  with  its  cell- wall,  protoplasm, 
and  chromatin  nucleus. 

To  sum  up,  the  existing  bacteria  exhibit  a  series  of  primor- 
dial physicochemical  phases  in  the  capture,  storage,  and  utiliza- 
tion of  energy,  and  in  the  development  of  products  useful  to 
themselves  and  to  other  organisms  and  of  by-products  which 


^Jordan,  Edwin  0.,  1908,  pp.  484-491. 


2 1.  J.  Kligler. 


88 


THE   ORIGIN  AND   EVOLUTION  OF  LIFE 


EVOLUTION  OF  BACTERIA 


89 


as  chemical  messengers  cause  interactions  in  other  organisms. 
With  the  simplest  bacteria  which  live  directly  on  the  lifeless 
world  we  find  that  most  of  the  fundamental  chemical  energies 
of  the  living  world  are  already  established,  namely: 

(a)  the  colloidal  cell  interior,  with  all  the  adaptations  of  col- 

loidal suspensions,  including 

(b)  the  stimulating  electric  action  and  reaction  of  the  metallic 

on  the  non-metallic  elements;  for  example,  the  accelera- 
tions by  iron,  manganese,  and  other  metals.  Some  bac- 
teria carry  positive,  others  negative  ion  charges; 

(c)  the  catalytic  messenger,  or  enzyme  action,  both  within  and 

without  the  organism; 

(d)  the  protein  and  carbon  energy  storage,  the  primary  food 

supply  of  the  living  world. 
Thus  the  chemical  reactions  of  bacteria  are  analogous  to  those 
^    of  the  higher  plant  and  animal  cells. 

Considering  bacteria  as  the  primordial  food  supply,  it  is 
the  invariable  presence  of  nitrogen  which  distinguishes  the 
bacteria  making  up  their  proteins;  nitrogen  is  also  a  large  con- 
stituent of  all  animal  j)roteins. 

Percentage  of  Elements  in  the  Proteins  ^ 


Carbon 50  0~55  o 

Hydrogen 6.9-  7.3 

Oxygen  19 . 0-24 . o 

Nitrogen 1 8.0-1 90 

Sulphur 0-3~  2} 


L 


Bacterial  suspensions  manifest  the  characteristics  of  col- 
loidal suspensions,  namely,  of  fluids  containing  minute  gelat- 
inous particles  which  are  kept  in  motion  by  molecular  move- 

'  Moore,  V.  J.,  191 5,  p.  199.     Nucleic  proteins  contain  a  notable  amount  of  phos- 
phorus as  well. 


I 


ment:  these  colloidal  substances  have  the  food-value  of  protein 
and  form  the  primary  food  of  many  Protozoa,  the  most  ele- 
mentary forms  of  animal  Hfe.  Chemical  messengers  in  the 
form  of  enzymes  of  three  kinds  exist,  proteolytic,  oxidizing,  and 
synthetic.'  The  proteolytic  enzymes  are  similar  to  the  tryptic 
enzymes  of  animals,  being  able  to  digest  only  the  proteoses 
and  simple  proteins  (casein,  albumin)  but  not  the  complex 
proteins.  Powerful  oxidizing  enzymes  are  present,  but  their 
character  is  not  known.  Synthetic  enzymes,  bringing  together 
new  living  chemical  compounds,  must  also  exist,  though  as  yet 
there  is  no  positive  information  concerning  them. 

Armed  with  these  physicochemical  powers,  which  may 
have  been  acquired  one  by  one,  the  primordial  bacteria  begin 
to  mimic  the  subsequent  evolution  of  the  higher  plant  and 
animal  world  by  an  adaptive  radiation  into  groups  which 
respectively  seek  new  sources  of  energy,  either  directly  from 
the  inorganic  world  or  parasitically  from  the  developing  organic 
bacterial  and  plant  foods  in  protein  and  carbohydrate  form, 
the  different  groups  living  together  in  large  communities  and 
interacting  chemically  upon  one  another  by  the  changes  pro- 
duced in  their  environment. 

The  iiarasitic  life  of  bacteria,  beginning  with  their  symbiotic 
relations  with  other  bacteria,  was  extended  into  intimate  rela- 
tions wilh  the  i>lants  and  finally  with  the  entire  living  world. 

Like  olher  forms  of  life,  bacteria  need  oxygen  for  combus- 
tion in  their  intracellular  actions  and  reactions;  but  free  oxygen 
is  nut  onh-  unnecessarv  but  actually  toxic  to  the  anaerobic 
bacteria,  discovered  by  Pasteur  In  1861,  which  derive  their 
oxygen  from  Inorganic  and  organic  compounds.  There  is, 
however,  a  transitional  group  of  bacteria,  known  as  the  faculta- 
tive anaerobes,  which  can  use  either  free  or  combined  oxygen, 

1 1.  J.  Kliglcr. 


-> 


I 


90 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


thus  forming  a  link  to  all  the  higher  forms  of  life  in  which  free 
oxygen  is  an  absolute  essential.  There  is  a  group  of  the  higher 
spore-forming  bacteria  which  must  have  free  oxygen.  These 
constitute  probably  a  late  stage  in  bacterial  evolution  and 
form  the  link  to  the  higher  forms. 

The  iron  bacteria  discovered  by  Ehrenberg  in  1838  obtain 
their  energy  from  the  oxidation  of  iron  compounds,  the  insolu- 
ble oxide  remaining  stored  in  the  cell  and  accumulating  into 
iron  as  the  bacteria  die.^  In  general  the  beds  of  iron  ore  found 
in  certain  of  the  pre-Cambrian  stratified  rocks,  which  have  an 
estimated  age  of  60,000,000  years,  are  believed  to  be  of  bac- 
terial origin.  Sulphur  bacteria  similarly  obtain  their  energy 
from  the  oxidation  of  hydrogen  sulphide. 

Bacteria  in  the  Balance  of  Life 

Bacteria  thus  anticipate  the  plant  world  of  algae,  diatoms, 
and  carbon-formers,  as  well  as  the  animal  world  of  Protozoa 
and  MoUusca,  by  playing  an  important  role  in  the  formation 
of  the  new  crust  of  the  earth.  This  is  observed  in  the  primor- 
dial limestone  depositions  composed  of  calcium  carbonate 
formed  by  bacterial  action  on  the  various  soluble  salts  of  cal- 
cium present  in  solution  in  sea-water,  a  process  exemplified 
to-day-  in  the  Great  Bahama  Banks,  where  chalk  mud  is  now 
precipitated  through  accumulation  by  B.  calcis.  Doubtless  in 
the  shallow  continental  seas  of  the  primal  earth  such  bacteria 
swarmed,  as  in  the  shallow  coastal  seas  of  to-day,  having  both 
the  power  of  secreting  and  precipitating  lime  and,  at  the  same 

^  It  is  claimed  that  iron  bacteria  play  an  important  part  in  the  formation  of  numerous 
small  deposits  of  bog-iron  ore,  and  it  seems  possible  that  their  activities  may  be  respon- 
sible for  extensive  sedimentary  deposits  as  well.  Further,  the  fact  of  finding  iron  bac- 
teria in  underground  mines  opens  the  possibility  that  certain  underground  deposits  of 
iron  ore  may  have  been  formed  by  them. — Harder,  E.  C,  IQIS,  p.  311. 

-  Drew,  George  IL,  1914,  p.  44. 


PROTOPLASM   AND   CHROMATIN 


91 


> 


time,  of  converting  nitrogen  combinations.  In  the  warm 
oceanic  waters  the  amount  of  lime  deposited  is  larger  and  the 
variety  of  living  forms  is  greater;  but  the  number  of  living  forms 
which  depend  for  food  on  the  algae  is  less  because  the  denitrify- 
ing bacteria  which  flourish  in  warm  tropical  waters  deprive  the 
algai  of  the  nitrates  so  necessary  for  their  development.  Again,  ^ 
where  algal  growth  is  scarce,  the  protozoic  unicellular  and 
multicellular  life  (plankton)  of  the  sea,  which  lives  upon  the 
alg£e,  is  also  less  abundant.  This  affords  an  excellent  illustra- 
tion of  the  great  law  of  the  balance  of  the  life  environment  through 
the  equilibrium  of  supply  of  energy,  one  aspect  of  the  interaction^ 
of  organisms  with  their  life  environment.  The  denitrifying 
bacteria  rob  the  waters  of  the  energy  needed  for  the  lowest 
forms  of  plants,  and  these  in  turn  are  not  available  for  the 
lowest  forms  of  animal  life.  Thus  in  the  colder  waters  of  the 
oceans,  where  the  denitrifying  bacteria  do  not  exist,  the  num- 
ber of  living  forms  is  far  greater,  although  their  variety  is  far 

less.^ 

The  so-called  luminous  bacteria  also  anticipate  the  plants 
and  animals  in  light  production,-  which  is  believed  to  be  con- 
nected with  the  oxidation  of  a  phosphorescing  substance  in 
the  presence  of  water  and  of  free  oxygen. 

Evolution  of  Protoplasm  and  Chromatin,  the  Two 
Structural  Components  of  the  Living  World 

It  is  still  a  matter  of  discussion"^  whether  any  bacteria,  even 
at  the  present  time,  have  reached  the  evolutionary  stage  of 
the  typical  cell  with  its  cell-wall,  its  contained  protoplasm,  and 
its  distinct  nuclear  form  and  inner  substance  known  as  chro- 
jnatin.     Some  bacteriologists  (Fischer)  maintain  that  bacteria\ 


»  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  1915,  p.  104. 
2  Harvey,  E.  Newton,  1915,  pp.  230,  238. 


3 1.  J.  Kligler. 


92 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


have  neither  nucleus  nor  chromatin;  others  admit  the  presence 
of  chromatin,  but  deny  the  existence  of  a  formal  nucleus;  others 
contend  that  the  entire  bacterial  cell  has  a  chromatin  content; 
while  still  others  claim  the  presence  of  a  distinctly  differenti- 
.  ated  nucleus  containing  chromatin.     Most  of  them,  however, 
are  agreed  as  to  the  presence  in  bacteria  of  granules  of  a  chro- 
matin nature,  while  they  leave  as  an  open  question  the  pres- 
\jence  or  absence  of  a  structurally  distinct  nucleus.     This  con- 
servative point  of  view  is  borne  out  by  the  fact  that  all  the 
common  bacteria  have  been  found  to  contain  nuclein,  the  spe- 
cific nuclear  protein   complex.      Nuclei   and   chromatin   were 
ascribed  to  the  Cyanophyccce,  by  KohP  as  early  as  1903  and 
\  by  Phillips-  and  by  OUve"^  in  1904. 

It  is  also  a  matter  of  controversy  among  bacteriologists 
whether  protoplasm  or  chromatin  is  the  more  ancient.     Cell 
observers  (Boveri,  Wilson,  Minchin),  however,  are  thoroughly 
agreed  on  this  point.     Thus  Minchin  is  unable  to  accept  any 
theory  of  the  evolution  of  the  earliest  forms  of  living  beings 
which  assumes  the  existence  of  forms  of  life  composed  entirely 
\  of  protoplasm  without  chromatin.^     All  the  results  of  modern 
investigations— the  combined  results,  that  is  to  say,  of  cytology 
and  protistology— appear  to  him  to  indicate  that  the  chroma- 
tin elements  represent  the  primary  and  original  living  units  or 
individuals,  and  that  the  protoplasm  represents  a  secondary 
product.     As  to  whether  chromatin  or  protoplasm  is  the  more 
ancient,   Boveri  suggests  that  true  cells  arose   through  sym- 
biosis between  protoplasm  and  chromatin,  and  that  the  chro- 
matin elements  were  primitively  independent,  living  symbioti- 
cally  with  protoplasm.     The   more  probable  view  is   that  of 
Wilson,  that  chromatin  and  protoplasm  are  coexistent  in  cells 


iKohl,  F.  G.,  1Q03.  =  Phillips,  O.  P.,  1904. 

*  Minchin,  E.  A.,  1916,  p.  32. 


'Olive,  E.  W.,  1904. 


PROTOPLASM  AND   CHROMATIN 


93 


from  the  earliest  known  stages,  in  the  bacteria  and  even  prob- 
ably in  the  ultramicroscopic  forms. 

The  development  of  the  celljheary  after  its  enunciation  in 
i-SjS^by  Schleiden  and  Schwann  followed  first  the  differentia- 


FiG.  1 2.    Protoplasm  (gray)  and  Chromatin  (black)  of  Amwba,  a  Typical  Protozoan. 

A  group  of  six  specimens  of  Amoeba  Umax  magnified  1000  diameters;  />  =  protoplasm; 

f//r.  =  chromatin  substance  of  nucleus;  7;  =  vacuoles. 

I  and  5.     Two  amoebae  with  the  chromatin  nucleus  (chr.)  in  the  "resting  stage." 

2.  An  amoeba  with  the  chromatin  nucleus  dividing  into  two  chromatin  nuclei. 

3.  A  parent  amteba  with  chromatin  nuclei  completely  separated. 

4.  Protoplasm  and  chromatin  nuclei  separated  to  form  two  young  amoebae. 

After  a  photograph  by  Gary  N.  Calkins. 

tion  of  protoplasmic  structure  in  the  cellular  tissues  (histology). 
Since  1880  it  has  taken  a  new  direction  in  investigating  the 
^  chemical  and  functional  separation  of  the  chromatin.  As  proto- 
plasm is  now  known  to  be  the  expression,  so  chromatin  is  now 
known  to  be  the  seat  of  heredity  which  Nageli  (1884)  was  the 
first  to  discuss  as  having  a  physicochemical  basis;  the  ''idio- 
plasm" postulated  in  his  theory  being  realized  in  the  actual 


94 


\ 


r^ 


c 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

structure  of  the  chromatin  as  developed  in 
the   researches  of   Hertwig,  Strasburger, 
KoUiker,  and  Weismann,  who   indepen- 
dently and  almost  simultaneously  (1884, 
1885)  were  led  to  the  conclusion  that  the 
nucleus  of  the  cell  contains  the  physical 
basis  of  inheritance  and  that  the  chroma- 
Xtin  is  its  essential  constituent.^     In  the 
development  from  unicellular  (Protozoa) 
into  multicellular    (Metazoa)    organisms 
the  chromatin  is  distributed  through  the 
nuclei  to  all  the  cells  of  the  body,  but 
Boveri   has   demonstrated    that   all    the 
body-cells  lose  a  portion  of  their  chroma- 
tin and   only   the  germ-cells   retain  the 
^entire  ancestral  heritage. 
/    Chemically,    the    most   characteristic 
peculiarity   of   chromatin    (Fig.    13),    as 

^  Wilson,  E.  B.,  1906,  p.  403- 

Fig.  13.    The  Two  Structural  Components  of 
THE  Living  World. 

Protoplasm  or  cytoplasm  represents  the  chief  visible  form 
or  substance  of  the  cell  in  the  grovvmg  condition  Chro- 
matin  is  the  chief  visible  centre  of  heredity;  there  are 
doubtless  other  visible  and  invisible  centres  of  energy 
concerned  in  heredity. 

Protoplasm  (grayish  dotted  areas)  and  Chromatin  (black 
waving  rods,  threads,  crescents,  and  Paired  spmdlcs)  in 
single  cells  {A-C)  and  in  clusters  of  cells  (£>,  h). 

A.  Achromaiium,  bacteria-like  organisms  with  network  of 
chromatin  threads  and  dots. 

B,  C.  Single-cell  eggs  in  the  ovaries  of  a  sea-urchin  (resting 
stage),  the  chromatin  concentrated  into  a  small 
black  sphere  within  the  nucleolus  (inner  circle). 

D.  Many  cells  in  the  root-tip  of  an  onion.     Chromatin 
(division  stage)  in  black,  wavy  lines  and  threads. 
E.  Many  cells  in  the  embryo  of  the  ^-t  redwoocMree  of  Cahfonjia.     Chn.mati^(div^^ 

stage)  in  black,  waving  rods   threads,  ^^7^^"^^' ^^^f^/^P  f  ,^^^^^^  Lawson. 

in  thin  black  lines  and  the  dotted  protoplasm  are  clearly  snoNvn. 


PROTOPLASM   AND   CHROMATIN 


95 


D 


r.     1^ 


contrasted  with  protoplasm,  is  its  phosphorus  content.^  It  is 
also  distinguished  by  a  strong  affinity  for  certain  stains  which 
cause  its  scattered  or  collected  particles  to  appear  intensely 
dark  (Fig.  13,  A-E).  /Nuclein,  which  is  probably  identical  with 
chromatin,  is  a  complex  albuminoid  substance  rich  in  phos- 
phorus.  The  chemical,  or  molecular  and  atomic,  constitution 
of  chromatin  infinitely  exceeds  in  complexity  that  of  any  other 
form  of  matter  or  energy  known.  As  intimated  above  (pp.  6,  77), 
it  not  improbably  contains  undetected  chemical  elements.  Ex- 
periments made  by/Oskar,  Gunther,  and  Paula  Hertwig  \1911- 
1914)  resulted  in  the  conclusion  that  in  cells  exposed  to  radium 
rays  the  seat  of  injury  is  chiefly,  if  not  exclusively,  in  the  chro-. 
matin:-  these  experiments  point  also  to  the  separate  and  dis- 
tinct chemical  constitution  of  the  chromatin. 

The  principle  formulated  by  Cuvier,  that  the  distinctive 
property  of  life  is  the  maintenance  of  the  individual  specific 
form  throughout  the  incessant  changes  of  matter  which  occur 
in  the  inflow  and  outflow  of  energy,  acquires  wider  scope  in 
the  law  of  the  continuity  of  the  germ-plasm  (z.  e.,  chromatin) 
announced  by  Weismann  in  1883,  for  it  is  in  the  heredity- 
chromatin**^  that  the  ideal  form  is  not  only  preserved,  but 
through  subdivision  carried  into  the  germ-cells  of  all  the 
present  and  succeeding  generations. 

It  would  appear,  according  to  this  interpretation,  that  the 
continuity  of  life  since  it  first  appeared  in  Archaeozoic  time  is 
the  continuity  of  the  physicochemical  energies  of  the  chroma- 
tin; the  development  of  the  individual  life  is  an  unfolding  of 
the  energies  taken  within  the  body  under  the  directing  agency 

*  Minchin,  E.  A.,  1916,  pp.  18,19.  ^  Richards,  A.,  1915,  p   291. 

'The  term  "  chromatin  "  or  "  hcredity-chromatin  "  as  here  used  is  equivalent  .0  the 
*'  germ-plasm  "  of  Weismann  or  the  "  stirp  "  of  Galton.  It  is  the  visible  centre  of  the 
energy  complex  of  heredity,  the  larger  part  of  which  is  by  its  nature  invisible.  Chro- 
matin, although  within  our  microscopic  vision,  is  to  be  conceived  as  a  gross  manifesta- 
tion of  the  infinite  energy  complex  of  heredity,  which  is  a  cosmos  in  itself. 


Fig.  14.    Bulk  of  Chromatin  in  Sequoia  and  Trillium  Comp^vred. 

Chromatin  rods  in  an  embryonic  cell  of  the  Sequoia  compared  with  those  in  an  embryonic  cell  of  the  small 
w^  Xnt  knoN^  as  tKrinity-aower  {Trillium).  The  chromatin  of  Sequom  {Sc.),  which  contains  all 
ThTcharaae^  t^entid  Ld  S    of  the  giant  tree,  is  less  in  bulk  than  the  chromatin  of  1  rtlh"m  {Tc.l  ,, 

s/Se^uoirJaSfn'Son/a   or  ,i,anUa,  the  Big  Tree  of  California,     The  ^I^-^^^g^^-^^.^^  "^^Jnd   i^  grTa^ 
shown  here,  is  ayg^^ff  feet  high  above  ground,  its  largest  circumference  is   102J  feet,  and   its  greatest 

Sc.  Part  ofihe  ge-^-ceU  of  the  nearly  allied  species.,S.,«.m  sempmirens  '^'jfZr^CtUaC  Slorln^Szc 
chromatin  roils  in  the  centre.     About  1,000  times  actual  size.     The  redwood  u.  but  little  mterior  m  size 

to  the   •  Big  Tree."     After  Goodspeed. 

Tc  ^Part"o7  the  germ  cell  of  Trillium  sessile,  showing  the  darkly  stained  chromatin  rods  in  the  same  phase  and 
with  the  same  magnification  as  in  the  cell  of  Sequoia.     After  Goodspeed. 

96 


PROTOPLASM  AND   CHROMATIN 


97 


of  the  chromatin;  and  the  evolution  of  Hfe  is  essentially  the 
evolution  of  the  chromatin  energies.     It  is  in  the  inconceivably 
physicochemical     complexity    of    the    microscopic    specks    of 
chromatin  that  life  presents  its  most  marked  contrast  to  anyy 
of  the  phenomena  observed  within  the  lifeless  world. 

Although  each  organism  has  its  specific  constant  in  the\ 
cubic  content  of  its  chromatin,  the  bulk  of  this  content  bears 
little  relation  to  the  size  of  the  individual.  This  is  illustrated 
by  a  comparison  of  the  chromatin  content  of  the  cell-nucleus 
of  Trillium,  a  plant  about  sixteen  inches  high,  with  that  of 
Sequoia  scmpervirens,  the  giant  redwood-tree  of  California, 
which  reaches  a  height  of  from  200  to  340  feet^  and  attains  an 
age  of  several  thousand  years  (Fig.  14);  we  observe  that  the 
chromatin  bulk  in  Sequoia  is  apparently  less  than  that  in 

Trillium. 

The  chromatin  content  of  such  a  nucleus  is  measured  by 
the  bulk  of  the  chromosome  rods  of  which  it  is  composed.  In 
the  sea-urchin  the  size  of  the  sperm-nucleus,  the  most  compact 
type  of  chromatin,  has  been  estimated  as  about  i  /ioo,ooo,ooo 
of  a  cubic  millimetre,  or  10  cubic  microns,  in  bulk.-  Within 
such  a  chromatin  bulk  there  is  yet  ample  space  for  an  incal- 
culable number  of  minute  particles  of  matter.  According  to  the^ 
figures  given  by  Rutherford^  in  the  first  Hale  Lecture  the  dia- 
meter of  the  sphere  of  action  of  an  atom  is  about  i  /ioo,ooo,ooo 

1  Jepson,  Willis  Linn,  191 1,  p.  23.  -  E.  B.  Wilson,  letter  of  June  28,  1916. 

3  It  is  necessary,  observes  Rutherford,  to  be  cautious  in  speaking  of  the  diameter  of 
an  atom,  for  it  is  not  at  all  certain  that  the  actual  atomic  structure  is  nearly  so  extensive 
as  the  region  through  which  the  atomic  forces  are  appreciable.  The  hydrogen  atom  is  the 
lightest  known  to  sdence,  and  the  average  diameter  of  an  atom  is  about  1/100,000,000 
of  a  centimetre;  but  the  negatively  charged  particles  known  as  electrons  are  about  1/1800 
of  the  mass  of  the  hydrogen  atom.  .  .  .  These  particles  travel  with  enormous  velocities 
of  from  10,000  to  100,000  miles  a  second.  .  .  .  The  alpha  particles  produce  from  the 
neutral  molecules  a  large  number  of  negatively  charged  particles  called  ions.  The  ioniza- 
tion due  to  these  alpha  particles  is  measurable.  ...  In  the  phosphorescence  of  an 
emanation  of  pure  radium  the  atoms  throw  off  the  alpha  particles  with  velocities  of 
10,000  miles  a  second,  and  each  second  five  billion  alpha  particles  are  projected.— Ruth- 
erford, Sir  Ernest,  191 5,  pp.  113,  128. 


98 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


of  a  centimetre,  or  1/10,000,000  of  a  millimetre,  or  1/10,000 
of  a  micron— the  unit  of  microscopic  measurement.  The  elec- 
trons released  from  atoms  of  matter  are  only  1/1800  of  the 
mass  of  the  hydrogen  atom,  the  lightest  known  to  science,  and 
thus  the  mass  of  an  electron  would  be  only  1/18,000,000  of  a 

micron. 

These  figures  help  us  in  some  measure  to  conceive  of  the 
chromatin  as  a  microcosm  made  up  of  an  almost  unlimited 
number  of  mutually  acting,  reacting,  and  interacting  particles; 
but  while  we  know  the  heredity-chromatin  to  be  the  physical 
basis  of  inheritance  and  the  presiding  genius  of  all  phases  of 
development,  we  cannot  form  the  slightest  conception  of  the 
mode  in  which  the  chromatin  speck  of  the  germ  cell  controls 
the  destinies  of  Sequoia  gigantea  and  lays  down  all  the  laws  of 
its  being  for  its  long  life  period  of  five  thousand  years. 

In  observing  the  trunk  of  "General  Sherman''  (Fig.  14), 
the  largest  and  oldest  living  thing  known,  one  finds  that  an 
active  regeneration  of  the  bark  and  woody  layers  is  still  in 
progress,  tending  to  heal  scars  caused  by  fire  many  centuries  ago. 
This  regeneration  is  attributable  to  the  action  of  the  heredity- 
chromatin  in  the  plant  tissues. 

We  are  equally  ignorant  as  to  how  the  chromatin  responds 
to  the  actions,  reactions,  and  interactions  of  the  body  cells,  of 
the  life  environment,  and  of  the  physical  environment,  so  as 
to  call  forth  a  new  adaptive  character,^  unless  it  be  through 
some  infinitely  complex  system  of  chemical  messengers  and 
other  catalytic  agencies  (p.  77).  Yet  in  pursuing  the  history 
of  the  evolution  of  life  upon  the  earth  we  may  constantly  keep 
before  us  our  fundamental  biologic  law-  that  the  causes  of 
evolution  are  to  be  sought  within  four  complexes  of  energies, 
which  are  partly  visible  and  partly  invisible,  namely: 

1  Wilson,  E.  B.,  1906,  p.  434-  ^  Osborn,  H.  F.,  1912.2. 


CHLOROPHYLL 


99 


' 


1.  Physicochemical  energies  in  the  evo- 

lution of  the  physical  environ- 
ment; 

2.  Physicochemical  energies  in  the  in- 

dividual development  of  the  or- 
ganism, namely,  of  its  protoplasm 
controlled  and  directed  by  its 
chromatin; 

3.  Physicochemical  energies  in  the  evo- 

lution of  the  heredity-chromatin 
with  its  constant  addition  of  new 
powers  and  energies; 

4.  Physicochemical  energies  in  the  evo- 

lution of  the  life  environment, 
beginning  with  the  protocellular 
chemical  organisms,  and  such  in- 
termediate organisms  as  bacteria, 
and  followed  by  such  cellular  and 
multicellular  organisms  as  the 
higher  plants  and  animals. 


Selection  and  Elimination 

Incessant  competition,  selection, 
intraselection  (Roux),  and  elim- 
ination between  all  parts  of  or- 
ganisms in  their  chromatin  ener- 
gies, in  their  protoplasmic  ener- 
gies, and  in  their  actions,  reac- 
tions, and  interactions  with  the 
living  environment  and  with  the 
physical  environment. 


\ 


V 


Chlorophyll  and  the  Energy  of  Sunlight 


As  bacteria  seek  their  energy  in  the  geosphere  and  hydro- 
sphere, chlorophyll  is  the  agent  which  connects  Ufe  with  the 
atmosphere,  disrupting  and  collecting  the  carbon  from  its  union 
with  oxygen  in  carbon  dioxide.  The  utilization  of  the  energy  \ 
of  sunlight  in  the  capture  of  carbon  from  the  atmosphere 
through  the  agency  of  chlorophyll  in  algae  marked  the  second 
great  phase  in  the  evolution  of  life,  following  the  first  bacterial^ 
phase.  This  capture  of  atmospheric  carbon,  the  chief  energy 
element  of  plants,  always  takes  place  in  the  presence  of  sun- 
light; while  the  chief  energy  elements  of  bacteria,  nitrogen  and 
(less  frequently)  carbon,  are  captured  through  molecule-splitting 
in  the  presence  of  heat,  but  without  the  powerful  aid  of  sun- 
light. 

It  is  the  metamorphosed,  fossilized  tissue  of  plants  which 
leads  us  to  the  conclusion  that  the  agency  of  chlorophyll  is 


M- 


lOO 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


also  extremely  ancient.  Near  the  base  of  the  Archaean  rocks^ 
graphites,  possibly  formed  from  fossilized  plant  tissue,  are 
observed  in  the  GrenviUe  series  and  in  the  Adirondacks.  The 
very  oldest  metamorphosed  sedimentaries  are  mainly  composed 
of  shales  containing  carbon  which  may  have  been  deposited  by 

plants. 

'^  As  a  reservoir  of  life  energy  which  is  liberated  by  oxidation, 
hydrogen  exceeds  any   other  element  in   the  heat  it  yields, 
namely,  34.5  calories  per  gram,  while  carbon  yields  8.1  calories 
\per    gram.-     Since    the    carbohydrates    constitute    the    basal 
energy-supply  of  the  entire  plant  and  animal  world,*^  we  may, 
with  reference  to  the  laws  of  action  and  reaction,  examine  the 
process  even  more  closely  than  we  have  done  above  (p.  51).    The 
results  of  the  most  recent  researches  are  presented  by  Wager  i-* 
'^The  plant  organ  responds  to  the  directive  influence  of 
light  by  a  curvature  which  places  it  either  in  a  direct  line  with 
the  rays  of  light,  as  in  grass  seedlings,  or  at  right  angles  to  the 
light,  as  in  ordinary  foliage  leaves."     ^^Of  the  light  that  falls 
upon  a  green  leaf  a  part  is  reflected  from  its  surface,  a  part  is 
transmitted,  and  another  part  is  absorbed.     That  which  is 
reflected  and  transmitted  gives  to  the  leaf  its  green  color;  that 
which  is  absorbed,  consisting  of  certain  red,  blue,  and  violet 
rays,  is  the  source  of  the  energy  by  means  of  which  the  leaf  is 
enabled  to  carry  on  its  work. 

''The  extraordinary  molecular  complexity  of  chlorophyll  has 
recently  been  made  clear  to  us  by  the  researches  of  Willstatter 
and  his  pupils;  Usher  and  Priestley  and  others  have  shown  us 
something  of  what  takes  place  in  chlorophyll  when  light  acts 
upon  it;  and  we  are  now  beginning  to  realize  more  fully  what 
a  very  complex   photosensitive  system  the   chlorophyll  must 


^  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  1915,  P-  545 


2  Henderson,  Lawrence  J.,  1913,  P-  245- 
*  Wager,  Harold,  1915,  p.  468. 


3  Moore,  F.  J.,  1915.  P-  213. 


EVOLUTION  OF  ALCE 


lOI 


i' 


be,  and  how  much  has  yet  to  be  accomplished  before  we  can 
picture  to  our  minds  with  any  degree  of  certainty  the  changes 
that  take  place  when  light  is  absorbed  by  it.  But  the  evidence 
afforded  by  the  action  of  light  upon  other  organic  compounds, 
especially  those  which,  like  chlorophyll,  are  fluorescent,  and 
the  conclusion  according  to  modern  physics  teaching  that  we 
may  regard  it  as  practically  certain  that  the  first  stage  in  any 
photochemical  reaction  consists  in  the  separation,  either  par- 
tial or  complete,  of  negative  electrons  under  the  influence  of 
light,  leads  us  to  conjecture  that,  when  absorbed  by  chloro- 
phyll, the  energy  of  the  light-waves  becomes  transformed  into 
the  energy  of  electrified  particles,  and  that  this  initiates  a  whole 
train  of  chemical  reactions  resulting  in  the  building  up  of  the 
complex  organic  molecules  which  are  the  ultimate  products  of 

the  plant's  activity." 

Chlorophyll  absorbs  most  vigorously  the  rays  between  ^\ 
and  C  of  the  solar  spectrum,^  which  are  the  most  energizing; 
the  effect  of  the  rays  between  D  and  E  is  minimal;  while  the, 
rays  beyond  F  again  become  effective.  As  compared  with  the 
primitive  bacteria  in  which  nitrogen  figures  so  largely,  chloro- 
phyllic  plant  tissues  consist  chiefly  of  carbon,  hydrogen,  and 
oxygen,  the  chief  substance  being  cellulose  (CeHioOs),'  while  in 
some  cases  small  amounts  of  nitrogen  are  found,  and  also  min- 
eral substances— potassium,  magnesium,  phosphorus,  sulphur, 
and  manganese.  ChlorophyUic  algal  Hfe  is  thus  in  contrast 
with  bacterial  life,  the  prime  function  of  which  is  to  capture 
nitrogen. 

Evolution  of  the  Alg^e 

Closest  to  the  bacteria  in  their  visible  structure  are  the  so^ 
called  ''blue-green  alga^"  or  Cyanophyceae,  found  almost  every- 

^  Loeb,  Jacques,  1906,  p.  115. 

*  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  1915,  p.  164. 


I02 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


where  in  fresh  and  salt  water  and  even  in  hot  springs,  as  well 
\as  on  damp  soil,  rocks,  and  bark.     The  characteristic  color  of 

the  Red  Sea  is  due  to  a 
free-floating  form  of 
these   blue-green    algae, 
which  in  this  case  are 
red.      Unlike    the    true 
algae,  the  cell-nucleus  of 
the    Cyanophyceae    or- 
dinarily is  not  sharply 
limited  by  a  membrane, 
and  there  is  no  evidence 
of    distinct    chlorophyll 
bodies,  although  chloro- 
phyll is  present.     In  the 
simpler   of    the    unicel- 
lular Cyanophyceae  the 
only  method  of  repro^ 
duction   is  that  known 
as  vegetative   multipli- 

FiG.  15.    Fossil  and  Living 
Alg.«  Compared 

C.  A  living  algal  pool  colony  near 

the  Great  Fountain  Geyser, 

Yellowstone    Park.      After 

Walcott. 

B.  Fossil  calcareous  algae,  Cryplo- 

zoon  prolifcrum  Hall,  from 

the   Cryptozoon   Ledge   in 

Lester  Park  near  Saratoga 

Springs,  N.  Y.     These  algae, 

which  are  among  the  oldest 

plants  of  the  earth,  grew  in  cabbage-shaped  heads  on  the  bottom  of  the  ancient 

Cambrian  sea  and  deposited  lime  in  their  tissue.     The  ledge  has  been  planed  down 

by  the  action  of  a  great  glacier  which  cut  the  plants  across,  showing  their  concentric 

interior  structure.     Photographed  by  H.  P.  Gushing. 

Fossil  algiE,  Nrd'landia  concentrica,  Newlandia  frondosa,  from  the  Algonkian  Belt 

Series  of  Montana.     After  Walcott. 


EVOLUTION  OF  ALG.E 


103 


V 


f 


cation,  in  which  an  ordinary  working  cell  (individual)  divides  / 
to  form  two  new  individuals.     In  certain  of  the  higher  forms, 
in  which  there  is  some  differentiation  of  connected  cells  and  in 
which  we  seem  justified  in  considering  the^'  individual"  to  b^ 
multicellular,  multiplication  is  accomplished  through  the  agency 
of  cells  of  special  character  known  as  the  spores.    No  evidences 
of  sexual  reproduction  have  been  observed  in  the  Cyanophyceae. 
The  sinter  deposits  of  hot  springs  and  geysers  in  Yellowstone 
Park  are  attributed  to  the  presence  of  Cyanophyceae. ^ 

With  the  appearance  of  the  true  alga3  the  earth-forming 
powers  of  life  become  still  more  manifest,  and  few  geologic 
discoveries   of   recent   times   are   more   important   than   those 
growing  out  of  the  recognition  of  algae  as  earth-forming  agents. 
As  early  as  1831  Lyell  remarked  their  rock-forming  powers. 
It  is  now  known  that  there  are  formations  in  which  the  algae 
rank  first  among  the  various  lower   organisms   concerned  in 
earth-building.     In  a  forthcoming  work  by  F.  W.  Clarke  and 
W.  C.  Wheeler,  they  remark  upon  these  earth-building  activ- 
ities as  follows:     "The  calcareous  algae  are  so  important  as 
reef-builders  that,  although  they  are  not  marine  invertebrates 
in  the  ordinary  acceptance  of  the  term,  it  seemed  eminently 
proper  to  include  them  in  this  investigation.     In  many  cases 
they  far  outrank   the  corals  in  importance,  and  of  late  years 
much  attention  has  been  paid  to  them.     On  the  atoll  of  Funa- 
futi, for  example,  the  algae  Lithothamnium  and  Halimeda  rank 
first  and  second  in  importance,  followed  by  the  foraminifera, 
third,  and  the  corals,  fourth.''  c^ 

Algse   are  probably   responsible  for   the  formation  of  the/i 
very  ancient  Umestones;  those  of  the  Grenville  series  at  the    > 
very  base  of  the  pre-Cambrian  are  believed  to  be  over  60,000,-  1 
000  years  of  age.     The  algal  flora  of  the  relatively  recent  Al- 

»  Coulter,  John  Merle,  1910,  pp.  10-14. 


I04 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


gonkian  time/  together  with  calcareous  bacteria,  developed 
the  massive  Hmestones  of  the  Tetons.  Clarke  observes:  ''We 
are  now  beginning  to  see  where  the  magnesia  of  the  limestones 
comes  from  and  the  algae  are  probably  the  most  important 
contributors  of  that  constituent." 

Thus  representatives  of  the  Rhodophyceae  contribute  as 
high  as  87  per  cent  of  calcium  carbonate  and  25  per  cent  of 
magnesium  carbonate.  Species  of  IJalimeda,  however,  calci- 
fied alga3  belonging  to  the  very  different  class  Chlorophyceae, 
are  important  agents  in  reef-building  and  land-forming,  yet  are 
almost  non-magnesian.- 

The  Grenville  series  at  the  base  of  the  Palaeozoic  is  essen- 
tially calcareous,  with  a  thickness  of  over  94,000  feet,  nearly 
eighteen  miles,  more  than  half  of  which  is  calcareous."^  Thus 
it  appears  probable  that  the  surface  of  the  primordial  conti- 
nental seas  swarmed  with  these  minute  algae,  which  served  as 
the  chief  food  magazine  for  the  floating  Protozoa;  bu£  it  is  very 
/important  to  note  that  algal  life  is  absolutely  dependent  upon 
phosphorus  and  other  earth-borne  constituents  of  sea-water,  as 
well  as  upon  nitrogen,  also  earth-borne,  and  due  to  bacterial 
action;  for  where  the  denitrifying  bacteria  rob  the  sea-water 
\of  its  nitrogen  content  the  algae  are  much  less  numerous.** 
Silica  is  also  an  earth-borne,  though  mineral,  constituent  of 
sea-water  which  forms  the  principal  skeletal  constituent  of  the 
shells  of  diatoms,  minute  floating  plants  especially  charac- 
teristic of  the  cooler  seas,  which  form  the  siliceous  ooze  of  the 
sea-bottoms. 

1  Walcott,  Charles  D.,  1914.  '  M.  A.  Howe,  letter  of  February  24,  1916. 

3  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  191 5,  PP-  545,  546. 
*   Op.  cit.,  p.  104. 


^ 


PLANT  AND  ANIMAL  EVOLUTION  105 

Some  Physicochemical  Contrasts  Between  Plant 

AND  Animal  Evolution 


) 


In  their  evolution,  while  there  is  a  continuous  specialization 
and  differentiation  of  the  modes  of  obtaining  energy,  plants 
may  not  attain  a  higher  chemical  stage  than  that  observed 
among  the  bacteria  and  alga;,  except  in  the  parasitic  forms 
which  feed  both  upon  plant  and  animal  compounds.     In  the 
energy  which  they  derive  from  the  soil  plants  continue  to  be 
closely  dependent  upon  bacteria,  because  they  derive  their 
nitrogen  from  nitrates  generated  by  bacteria  and   absorbed 
along  with  water  by  the  roots.     In  reaching  out  into  the  air 
and  sunlight  the  chlorophyllic  organs  differentiate  into   the 
marvellous  variety  of  leaf  forms,  and  these  in  turn  are  sup- 
ported upon  stems  and  branches  which  finally  lead  into  the 
creation  of  woody  tissues  and  the  clothing  of  the  earth  with 
forests.     Through  the  specialization  of  leaves  in  connection 
with  the  germ-cells  flowers  are  developed,  and  plants  establish 
a  marvellous  series  of  balanced  relations  with  their  life  environ- 
ment, first  with  the  developing  insect  life,  and  finally  with  the 

developing  bird  life. 

The  main  lines  of  the  ascent  and  classification  of  plants  are 
traced  by  palajobotanists  partly  from  their  structural  evolu- 
tion, which  is  almost  invariably  adapted  to  keep  their  chloro- 
phyllic organs  in  the  sunlight'  in  competition  with  other  plants, 
and  partly  from  the  evolution  of  their  reproductive  organs, 
which  pass  through  the  primitive  spore  stage  into  various 
forms  of  sexuality,  with,  finally,  the  development  of  the  seed 
habit  and  the  dominance  of  the  sporophyte.^  It  is  a  striking 
peculiarity  of  plants  that  the  powers  of  motion  evolve  chiefly 
in  connection  with  their  reproductive  activities,  namely,  with 

I  Wager,  Harold,  .9>S,  P-  468.  '"  M.  A.  Howe. 


io6 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


PLANT  AND   ANIMAL  EVOLUTION 


107 


the  movements  of  the  germ  cells.  We  follow  the  development 
of  a  great  variety  of  automatic  migrating  organs,  especially  in 
the  seed  and  embryonic  stages,  by  which  the  germs,  or  chro- 
matin bearers,  are  mechanically  propelled  through  the  air  or 
water.  Plants  are  otherwise  dependent  on  the  motion  of  the 
atmosphere  and  of  animals  to  which  they  become  attached 
for  the  migration  of  their  germs  and  embryos  and  of  their 
adult  forms  into  favorable  conditions  of  environment.  In 
these  respects  and  in  their  fundamentally  different  sources  of 
energy  they  present  the  widest  contrast  to  animal  evolution. 

In  the  absence  of  a  nervous  system  the  remarkable  actions 
and  reactions  to  environmental  stimuli  which  plants  exhibit 
are  purely  of  a  physicochemical  nature.     The  interactions  be- 
tween different  tissues  of  plants,  which  become  extraordinarily 
complex  in  the  higher  and  larger  forms,  are  probably  sustained 
through  catalysis  and  the  circulation  through  the  tissues  of 
chemical  messengers  analogous  to  the  enzymes,  hormones  (ac- 
celerators), and  chalones  (retarders)  of  the  animal  circulation. 
It  is  a  very  striking  feature  of  plant  development  and  evolu- 
'    tion  that,  although  entirely  without  the  coordinating  agency 
of  a  nervous  system,  all  parts  are  kept  in  a  condition  of  perfect 
^  correlation.     This  fact  is  consistent  with   the  comparatively 
recent  discovery  that  a  large  part  of  the  coordination  of  animal 
organs  and  tissues  which  was  formerly  attributed  to  the  ner- 
\vous  system  is  now  known  to  be  catalytic. 

Throughout  the  evolution  of  plants  the  fundamental  dis- 
tinctions between  the  heredity-chromatin  and  the  body-proto- 
plasm are  sustained  exactly  as  among  animals. 

It  would  appear  from  the  researches  of  de  Vries^  and  other 

botanists  that  the  sudden  hereditary  alterations  of  plant  struc- 

/ture  and  function  which  may  be  known  as  mutations  of  de 

»  De  Vries,  Hugo,  iqoi,  1Q03,  1905. 


Vries^   are   of   more    general   occurrence    among   plants   than 
among  animals.     Such  mutations  are  attributable  to  sudden 
alterations  of  molecular  and  atomic  constitution  in  the  hered- 
ity-chromatin, or  to  the  altered  forms  of  energy  supplied  to^ 
the  chromatin  during  development.     Sensitiveness  to  the  bio- 
chemical reactions  of  the  physical  environment  should  theo- 
retically be  more  evident  in  organisms  like  plants  which  derive 
their  energy  directly  from  inorganic  compounds  that  are  con- 
stantly changing  their  chemical  formulae  with  the  conditions 
of  moisture,  of  aridity,  of  temperature,  of  chemical  soil  con- 
tent, than  in  organisms  like  animals  which  secure  their  food 
compounds   ready-made  by   the  plants  and  possessing   com- 
paratively similar  and  stable  chemical  formulae.     Thus  a  plant\ 
transferred  from  one  environment  to  another  may  exhibit  much 
more  sudden  and  profound  changes  than  an  animal,  for  the 
reason   that  all   the  sources  of  plant  energy  are  profoundly 
changed  while  the  sources  of  animal  energy  in  a  new  environ-^ 
ment  are  only  slightly  changed.      The  highly  varied  chemical 
sources  of  plant  energy  are  in  striking  contrast  with  the  com- 
paratively uniform  sources  of  animal  energy  which  are  primarily 
the  starches,  sugars,  and  proteins  formed  by  the  plants. 

In  respect  to  character  origin,  or  the  appearance  of  new\ 
characters,  therefore,  plants  may  in  accordance  with  the  de 
Vries  mutation  hypothesis  exhibit  discontinuity  or  sudden 
changes  of  form  and  function  more  frequently  than  animals./ 
In  respect  to  character  coordination,  or  the  harmonious  relations 
of  all  their  parts,  plants  are  inferior  to  animals  only  in  their 
sole  dependence  on  catalytic  chemical  messengers,  while  animal 
characters  are  coordinated  both  through  catalytic  chemical 
messengers  and  through  the  nervous  system. 

In  respect  to  characUr  velocity,  or  the  relative  rates  of  move- 

» As  distinguished  from  the  earlier  defined  Mutations  of  Waagen  (see  p.  138). 


/ 


io8  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

ment  of  different  parts  of  plants  in  individual  development 
and  in  evolution,  plants  appear  to  agree  very  closely  with 
animals.  In  both  we  observe  that  some  characters  evolve  more 
rapidly  or  more  slowly  than  others  in  geologic  time;  also  that 
some  characters  develop  more  rapidly  or  slowly  than  others  in 
the  course  of  individual  growth.  This  may  be  termed  charac- 
ter motion  or  character  velocity. 

This  law  of  changes  in  character  velocity,  both  in  individ- 
ual development  (ontogeny)  and  in  racial  evolution  (phylog- 
eny),  is  one  of  the  most  mysterious  and  difficult  to  understand 
Mn  the  whole  order  of  biologic  phenomena.     One  character  is 
hurried  forward  so  that  it  appears  in  earlier  and  earlier  stages 
of  individual  development  (Hyatt's  law  of  acceleration),  while 
another  is  held  back  so  that  it  appears   in   later  and  later 
\ stages  (Hyatt's  law  of  retardation).     Osborn  has  also  pointed 
out  that  corresponding  characters  have  different  velocities  in 
different  lines  of  descent— a  character  may  evolve  very  rapidly 
in  one  line  and  very  slowly  in  another.     This  is  distinctively  a 
heredity-chromatin  phenomenon,  although  visible  in  protoplas- 
mic form.     Among  plants  it  is  illustrated  by  the  recent  obser- 
vations of  Coulter  on  the  relative  time  of  appearance  of  the 
archegonia  in  the   two  great  groups  of  gymnosperms   {i.  e., 
naked-seeded  plants),  the  Cycads  (sago-palms,  etc.)  and  the 
Conifers  (pines,  spruces,  etc.),  as  follows: In  the  Cycads,  which 
are  confined  to  warmer  climates,  the  belated  appearance  of  the 
^  archegonium  persists;  in  the  Conifers,  in  adaptation  to  colder 
climates  and  the  shortened  reproductive  season,  the  appearance 
of  the  archegonium  is  thrust  forward  into  the  early  embryonic 
stages.     Finally,  in  the  flowering  plants   (Angiosperms)  with 
their  brief  reproductive  season,  the  forward  movement  of  the 
archegonium  continues  until  the  third  cellular  stage  of  the  em- 
X  bryo  is  reached.     This  is  but  one  illustration  among  hundreds 


PLANT  AND   ANIMAL  EVOLUTION 


109 


0 


which   might   be   chosen  to  show  how  character  velocity  in 
plants  follows  exactly  the  same  laws  as  in  animals,  namely, 
characters  are  accelerated  or  retarded  in  race  evolution  and  in\ 
individual  development  in  adaptation  to  the  environmental  and 
individual  needs  of  the  organism. 

We  shall  see  this  mysterious  law  of  character  velocity 
beautifully  illustrated  among  the  vertebrates,  where  of  two 
characters,  lying  side  by  side,  one  exhibits  inertia,  the  other 
momentum. 

It  is  difficult  to  resist  the  speculation  that  character  velocity 
in  individual  development  and  in  evolution  is  also  a  phenom- 
enon of  physicochemical  interaction  in  some  way  connected 
with  and  under  the  control  of  chemical  messengers  which  are 
circulating  in  the  system. 


h 


PART  II.     THE  EVOLUTION  OF  ANIMAL  FORM 


CHAPTER  IV 

THE  ORIGINS  OF  ANIMAL  LIFE  AND  EVOLUTION 

OF  THE  INVERTEBRATES 

Evolution  of  single-celled  animals  or  Protozoa.  Evolution  of  many-celled 
animals  or  Metazoa.  Pre-Cambrian  and  Cambrian  forms  of  Inverte- 
brates. Reactions  to  climatic  and  other  environmental  changes  of  geo- 
logic time.     The  mutations  of  Waagen. 

A  prime  biochemical  characteristic  in  the  origin  of  animal 
life  is  the  derivation  of  energy  neither  directly  from  the  water, 
from  the  earth,  nor  from  the  earth's  or  sun's  heat,  as  in  the 
most  primitive  bacterial  stages;  nor  from  sunshine,  as  in  the 
chlorophyllic  stage  of  plant  life;  but  from  its  stored  form  in 
the  bacterial  and  plant  world.  All  animal  life  is  chemically 
dependent  upon  bacterial  and  plant  life. 

Many  of  the  single-celled  animals  like  the  single-celled  bac- 
teria and  plants   appear   to  act,  react,  and   interact   directly 
with  their  lifeless  and  life  environment,  their  protoplasm  be- 
ing relatively  so  simple.     We  do  not  know  how  far  this  action, 
reaction,  and  interaction  affects  the  protoplasm  only,  and  how 
far  it  affects  both  protoplasm  and  chromatin.     It  would  seem 
as  if  even  at  this  early  stage  of  evolution  the  organism-proto- 
plasm was  sensitive  while  the  heredity- chromatin  was  relatively 
insensitive  to  environment,  stable,  and  as  capable  of  conserving 
and  reproducing  hereditary  characters  true  to  type  as  in  the 
many-celled  animals  in  which  the  heredity-chromatin  is  deeply 
buried  within  the  tissues  of  the  organism  remote  from  direct 
environmental  reactions. 


no 


EVOLUTION  OF  PROTOZOA 


III 


Evolution  of  Single-Celled  Animals  or  Protozoa 

We  have  no  idea  when  the  first  unicellular  animals  known 
as  Protozoa  appeared.  Since  the  Protozoa  feed  freely  upon^ 
bacteria,  it  is  possible  they  may  have  evolved  during  the  bac- 
terial epoch;  it  is  known  that  Protozoa  are  at  present  one  of 
the  limiting  factors  of  bacterial  activity  in  the  soil,  and  it  is 
even  claimed^  that  they  have  a  material  effect  on  the  fertility 
of  the  soil  through  the  consumption  of  nitrifying  bacteria. 

On  the  other  hand,  it  may  be  that  the  Protozoa  appeared 
during  the  algal  epoch  or  subsequent  to  the  chlorophyllic  plant 
organisms  which  now  form  the  primary  food  supply  of  the 
freely  floating  and  swimming  protozoan  types.  A  great  num- 
ber of  primitive  flagellates  are  saprophytic,  using  only  dis- 
solved proteids  as  food.- 

Apart  from  the  parasitic  mode  of  deriving  their  energy, 
even  the  lowest  forms  of  animal  life  are  distinguished  both  in 
the  embryonic  and  adult  stages  by  their  locomotive  powers. 
Heliotropic  or  sun  reactions,  or  movements  toward  sunlight, 
are  manifested  at  an  early  stage  of  animal  evolution.  In  this 
function  there  appear  to  be  no  boundaries  between  animals 
and  the  motile  spores,  gametes,  and  seedlings  of  certain  plants.^ 
As  cited  by  Loeb  and  Wasteneys,  Paul  Bert  in  1869  discovered 
that  the  little  water-flea  Daphnia  swims  tow^ard  the  light  in  all 
parts  of  the  visible  spectrum,  but  most  rapidly  in  the  yellow  or 
in  the  green.  More  definitely,  Loeb  observes  that  there  are  \ 
two  particular  regions  of  the  spectrum,  the  rays  of  which  are 
especially  effective  in  causing  organisms  to  turn,  or  to  congre- 
gate, toward  them;    these  regions  lie   (i)   in  the  blue,  in  the 

^Russell,  Edward  John,  and  Hutchinson,  Henry  Brougham,  1909,  p.  118;    1913,  pp. 
191,  219. 

*  Gary  N.  Calkins. 

'  Loeb,  Jacques,  and  Wasteneys,  Hardolph,  1915.1,  pp.  44-47;  1915.2,  pp.  328-330. 


li 

h 


A. 


Fig    i6     Typical  Forms  of  Protozoa  or  Single-Celled  Organisms. 

tory.    They  are  distinguished  by  one  or  more  wh,p4,k    P-'-«»^- ;^:,'^?:^„t,:%hrrac,e'ris^body 

IrrT^d  have\rrtl"ono:d  i„l::r^n  Z^l:l^  area  or  .he  U».y.     Ma.„if,c^  .8s  .in,es 

lite-size.     Photographed  (rom  a  model  in  -'>'%-^7"'""iM«irrms  dislioRuished  by  a  multitude  of  fine 
A  typical  ciliate,  one  of  the  most  ^whly  orsan.zed  s  ng  e<eH^^^^^  Jl„c„motion  an,l  for 

rStt^e^i  ;::::r.ntme"  riS  :^  rrt^ou^  or  s^lalUea  for  further  effectiveness.     After 
ButschlL     Magnified  i8o  times  hfe-size. 

112 


E 


EVOLUTION  OF  PROTOZOA 


113 


neighborhood  of  a  wave-length  of  477  /^m,  and  (2)  in  the 
yellowish-green,  in  the  region  of  X  =  534  MM;  and  these  two 
wave-lengths  affect  different  organisms,  with  no  very  evident 
relation  to  the  nature  of  these  latter.  Thus  the  blue  rays 
(of  477  fJLfj)  attract  the  protozoan  flagellate  Euglena,  the  hydroid 


HEAT     LIG 


CHEMIC4L 


INFRil    RED 


Billion  vibraivf^  f^*"  secofui 


VLTRA   VIOLET 


Fig.  17.    Light,  Heat,  and  Chemical  Influence  of  the  Sun. 

Diagram  showing  the  increase,  maximum,  and  decrease  of  heat,  light,  and  chemical 
energy  derived  from  the  sun.  The  shaded  area  represents  that  portion  of  the  spec- 
trum included  in  the  phosphorescent  light  emitted  by  our  common  fire-flies.  It  is 
probable  that  it  corresponds  more  closely  with  the  light  sensitiveness  of  the  fire-fly's 
eye  than  with  that  of  the  human  eye  as  represented  by  the  wave  marked  "Light." 
After  Ulric  Dahlgren. 

coclenterate  Endendrium,  and  the  seedlings  of  oats;  while  the 
yellowish-green  rays  (of  534  P^y)  in  turn  affect  the  protozoan 
Chlamydomonas,  the  crustacean  Daphnia,.  and  the  crustacean 

larvae  of  barnacles. 

Aside  from  these  heliotropic  movements  which  they  share 
with  plants,  animals  show  higher  powers  of  mdividuality,  of 
initiation,  of  experiment,  and  of  what  Jennings  cautiously 
terms  ^>  conscious  aspect  of  behavior."  In  his  remarkable 
studies  this  author  traces   the  genesis  of  animal  behavior  to 


114  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

reaction  and  trial.     Thus  the  behavior  of  organisms  is  of  such 
a  character  as  to  provide  for  its  own  development.     Through 
the  principle  of  the  production  of  varied  movements  and  that 
of  the  resolution  of  one  physiological  state  into  another,  any- 
thing that  is  possible  is  tried  and  anything  that  turns  out  to 
be  advantageous  is  held  and  made  permanent.'     Thus  the  sub- 
psychic  stages  when  they  evolve  into  the  higher  stages  give  us 
the  rudiments  of  discrimination,   of  choice,   of  attention,  of 
desire  for  food,  of  sensitiveness  to  pain,  and  also  give  us  the 
foundation  of  the  psychic  properties  of  habit,  of  memory,  and 
of    consciousness.^    These    profound    and    extremely    ancient 
powers  of  animal  life  exert  indirectly  a  creative  influence  on 
animal  form,  whether  we  adopt  the  Lamarckian  or  Darwinian 
explanation  of  the  origin  of  animal  form,  or  find  elements  of 
truth  in  both  explanations.'    The  reason  is  that  choice,  dis- 
crimination,   attention,    desire   for   food,    and   other   psychic 
powers  are  constantly  acting  on  individual  development  and 
directing  its  course.     Such  action  in  turn  controls  the  habits 
and  migrations  of  animals,  which  finally  influence  the  laws  of 
adaptive  radiation*  and  of  selection.     In  this  indirect  way  these 
psychic  powers  are  creative  of  new  form  and  new  function. 
In  the  evolution  of  the  Protozoa^  the  starting-point  is  a 
/  simple  cell  consisting  of  a  small  mass  of  protoplasm  contain- 
ing   a    nucleus    withm    which    lies    the    heredity-chromatin 
(Fig.   12).      This    passes    into    the    plasmodial    condition    of 
the  Rhiwpods,  in  which  the  protoplasm  increases  enormously 
to  form  the  relatively  large,  unprotected  masses  adapted  to 

.  Jennings,  H.S.,  1906,  pp.  3.8.  3.9.  ^,        ,  '^^^   M  in^he'lMX- 

» These  two  explanations  are  fully  set  forth  below  (see  pp.  143-146)  m  the  introduc- 
tion to  the  evolution  of  the  vertebrates.  ,  -        .      i„  „_,„. 

.  Uaptive  radialion-tho  development  of  widely  divergent  orms  m  animals  ances- 
trally ol  the  same  stock  or  of  related  stocks,  as  a  result  of  bodily  adaptation  to  widely 
different  environments  (see  p.  157)- 

5  Minchin,  E.  A.,  1916,  p.  277. 


EVOLUTION  OF  PROTOZOA 


IIS 


the  creeping  or  semiterrestrial  mode  of  life.  From  these 
evolve  the  forms  specialized  for  the  floating  pelagic  habit, 
namely,  the  Foraminifera  and  Radiolaria,  protected  by  an 
excessive  development  and  elaboration  of  their  skeletal  struc- 
tures.^    Less   cautious   observers^   than   Jennings   find   in   the 


/ 


Fig.  18.    Skeletons  of  Typical  Protozoa. 

B  Siliceous  skeleton  or  shell  of  a  typical  radiolarian,  Stauraspis  stauracantha  Haeckel, 
170  times  the  actual  size.  Owing  to  their  vast  numbers,  these  microscopic,  glassy 
skeletons  are  an  appreciable  factor  in  earth-building.  A  large  part  of  the  island 
of  Barbados  is  formed  of  radiolarian  ooze.     Photographed  from  a  model  m  the 

American  Museum.  .       ,   „  . ,      j,r\  w 

C  Calcareous  skeleton  or  shell  of  a  typical  foraminifer,  Globigertnabulotdcs  d  Orbigny, 
■  .0  times  the  actual  size.  As  the  animal  increases  in  size  it  forms  successively 
larger  shells  adjoining  the  earlier  ones  until,  as  shown  in  the  figure,  a  cluster  of 
shells  of  increasing  size  is  formed.  The  name  foraminifer  refers  to  the  many 
minute  openings,  plainly  seen  in  this  figure,  through  which  the  pseudopodia  can 
pass.  Photographed  from  a  model  in  the  American  Museum.  (Compare  I'lg.  16, 
p.  112.) 

Foraminifera  the  rudiments  of  the  highest  functions  and  the 
most  inteUigent  behavior  of  which  undifferentiated  protoplasm 
has  been  found  capable.  In  the  Mastigophora  the  body  de-\ 
velops  flagellate  organs  of  locomotion  and  food-capture.  As 
an  offshoot  from  the  ancestors  of  these  forms  arose  the  Ciliata, 
the  most  highly  organized  unicellular  types  of  living  beings/ 


^  op.  oil.,  9.  278. 


2  Heron-Allen,  Edward,  1915,  P-  270. 


\ 


\ 


ii6  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

for  a  Ciliate,  like  every  other  protozoan,  is  a  complete  and 
independent  organism,  and  is  specialized  for  each  and  all  of 
the  vital  functions  performed  by  the  higher  multicellular  or- 
ganisms as  a  whole. 

In  the  chemical  life  of  the  Protozoa>  {Amceha)  the  proto- 
plasm is  made  up  of  colloidal  and  of  crystalloidal  substances 
of  different  density,  between  which  there  is  a  constant,  orderly 
chemical  activity.     The  relative  speed  of  these  orderly  proc- 
esses is  attributed  to  specific  catalyzers  which  control  each 
successive  step  in  the  long  chain  of  chemical  actions.     Thus 
in  the  breaking-down  process  (destructive  metabolism)  the  by- 
products act  as  poisons  to  other  organisms  or  they  may  play 
an  important  part  in  the  vital  activities  of  the  organism  itself, 
as  in  the  phosphorescence  of  Noctiluca,  or  as  in  reproduction 
and  regeneration.     Since  regrowth  or  regeneration^  takes  place 
in  artificially  separated  fragments  of  cells  in  which  the  nuclear 
substance  (chromatin)  is  believed  to  be  absent,  the  formation 
of  new  parts  may  be  due  to  a  specific  enzyme,  or  perhaps  to 
some  chemical  body  analogous  to  hormones  and  formed  as  a 
result  of  mutual  interaction  of  the  nucleus  and  the  protoplasm. 
Reproduction  through  cell-division  is  also  interpreted  theoreti- 
cally as  due  to  action  set  up  by  enzymes  or  other  chemical 
bodies  produced  as  a  result  of  interaction  between  the  nucleus 
and  cell  body.    The  protoplasm  is  regenerated,  including  both 
the  nuclei  and  the  cell-plasm,  by  the  distribution  of  large  quan- 
tities   of    nucleoproteins,   the    specific   chemical   substance  of 

chromatin. 

The  latest  word  as  to  the  part  played  by  natural  selection 
in  the  heredity-chromatin  is  that  of  Jennings-^  who,  after  many 
years  of  experiment,  has  proved  that  the  congenital  charac- 


V 


1  Calkins,  Gary  N.,  1916,  p.  260. 
3  Jennings,  H.  S.,  1916,  pp.  522-526. 


2  Op.  cit.,  pp.  261-264,  266. 


EVOLUTION  OF  METAZOA 


117 


\ 


/ 


ters  arising  from  the  heredity-chromatin  are  changed  by  long- 
continued  selection  through  a  great  number  of  generations  in 
the  form  of  slow  gradations  which  would  not  be  revealed  by  / 
imperfect  selection  for  a  few  generations.     This  is  doubtless 
the  way  in  which  nature  works.     In  the  protozoan  known  as 
Diffiugia  the  inherited  changes  produced  by  selection  seem  as 
gradual  as  could  well  be  observed.     Large  steps  do  occur,  but 
much  more  frequent  is  the  slow  alteration  of  the  stock  with 
the  passage  of  generations.     The  question  is  asked  whether 
even  such  slight  and  seemingly  gradual  hereditary  changes 
may  not  really  be  little  jumps  or  mutations,  since  all  chemical 
change  is  discontinuous.     In  reply,  Jennings  observes  that  it  is^ 
highly  probable  that  every  inherited  variation  does  involve  a 
chemical  change,  for  there  is  no  character  change  so  slight  that^ 
it  may  not  be  chemical  in  nature.     In  the  relatively  immense 
organic  molecule,  with  its  thousands  of  groups,  the  simple  trans- 
fer of  one  atom,  one  ion,  perhaps  one  electron,  is  a  chemical 
change  and,  in  this  sense,  discontinuous  even  though  its  effect 
is  below  our  powers  of  perception  with  the  most  refined  instru- 
ments. 

Through  this  modern  chemical  interpretation  of  the  pro- 
tozoan life  cycle  we  may  conceive  how  the  laws  of  thermody- 
namics may  be  applied  to  single-celled  organisms,  and  espe- 
cially our  fundamental  biologic  law  of  action,  reaction,  and  inter- 
action. By  far  the  most  difficult  problem  in  biologic  evolution 
is  the  mode  of  working  of  this  law  among  the  many-celled  or- 
ganisms (Metazoa)  including  both  invertebrates  and  vertebrates. 

Evolution  of  Many- Celled  Animals  or  Metazoa 

It  is  possible  that  during  the  long  period  of  pre-Cambrian  \^ 
time,  which,  from  the  actual  thickness  of  the  Canadian  pre- 
Cambrian  rocks,  is  estimated  at  not  less  than  thirty  million 


ii 


Phyla  of  Fossil  ^ 
Invertebrata 

Protozoa, 

Porifera, 

Coelenterata, 

Molluscoida, 

Echinodermata, 

Annulata, 

Arthropoda, 

Mollusca. 


ii8  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

years,  some  of  the  simpler  Protozoa  gave  rise  to  the  next  higher 
stage  of  animal  evolution  and  to  the  adaptive  radiation  on 
land  and  sea  of  the  Invertebrata. 

We  are  compelled  to  assume  that  the  physicochemical  actions, 
reactions,  and  interactions  were  sustained  and  became  step  by 
step  more  complex  as  the  single-celled 
life  forms  (Protozoa)  evolved  into  or- 
ganisms with  groups  of  cells  (Metazoa), 
and  these  into  organisms  with  two  chief 
cell-layers  (Coelenterata),  and  later 
into  organisms  with  three  chief  cell- 
layers. 

The   metamorphosis   by   heat   and 
pressure  of  the  pre-Cambrian  rocks  has 
for  the  most  part  concealed  or  destroyed  all  the  life  impressions 
which  were  undoubtedly  made  in  the  various  continental  or 
oceanic   basins   of   sedimentation.     Indirect   evidences   of   the 
long  process  of  Ufe  evolution  are  found  in  the  great  accumula- 
tions of  limestone  and  in  the  deposits  of  iron  and  graphite^ 
which,  as  we  have  already  observed,  are  considered  proofs  of 
the    existence    at    enormously    remote    periods    of    Umestone- 
forming  alg^,  of  iron-forming  bacteria,  and  of  a  variety  of 
chlorophyll-bearing  plants.     These  evidences  begin  with   the 
metamorphosed  sedimentaries  overlying  the  basal  rocks  of  the 
crust  of  the  primal  earth. 

Pre-Cambrian  and  Cambrian  Forms  of  Invertebrates 

The  discovery  by  Walcott^  of  a  world  of  highly  specialized 
and  diversified  invertebrate  life  in  the  Middle  Cambrian  seas 
completely  confirms  the  prophecy  made  by  Charles  Darwm  m 

1  Joseph  Barren.     See  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  1915,  P-  547- 

2  Walcott,  Charles  D.,  1911,  1912. 


CAMBRIAN  INVERTEBRATES 


119 


^ 


* 


1859^  as  to  the  great  duration  that  must  be  assigned  to  pre- 
Cambrian  time  to  allow  for  the  evolution  of  highly  specialized 

life  forms. 

By  Middle  Cambrian  time  the  adaptive  radiation  of  the 
Invertebrata  to  all  the  conditions  of  life— in  continental  waters, 


PALEOGEOOI,APHY.  LATE  LOWER  CAMBR.AH  (WAUCOBIAN  OR  OLENELLUS.  TIME 

AFTER  SCHUCHERT,  APRIL,  191« 

„  .„_  .«  MOUNTAINS  A  •  ARCHAEOCYATHINAE 

^UARINt  DEPOSITS  XACT.VE  VOLCANOES  .N  SCOTLAND  .      MOUNTAINS _ 


Fig    t9.    Theoretic  World  Environment  in  Late  Lower  Cambrian  Time. 
This  period  corresponds  with  that  of  the  first  -"^^^ -^'^^ Jl^^k^tV  -  "'^^ 

along  the  shore-lines,  and  in  the  littoral  and  pelagic  environ- 
ment of  the  seas-appears  to  have  been  governed  by  mechan- 
ical and  chemical  principles  fundamentally  similar  to  those 
observed  among  the  Protozoa,  but  distributed  through  myr^ds 
of  cells  and  highly  complicated  tissues  and  organs,  mstead  of 
being  differentiated  within  a  single  cell  as  in  the  cihate  Pro- 
tozoa.    Among  the  elaborate  functions  thus  evolved,  showing 

1  Darwin.  Charles,  1850,  pp.  306,  307. 


•  • 


I20 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


a  more  complicated  system  of  action,  reaction,  and  interaction 
with  the  environment  and  within  the  organism,  were,  first, 
a  more  efficient  locomotion  in  the  quest  of  food,  in  the  capture 
of  food,  and  in  the  escape  from  enemies,  giving  rise  in  some 
cases  to  skeletal  structures  of  various  types;  second,  the  evolu- 
tion of  offensive  and  defensive  weapons  and  armature;  third, 
various  chemical  modes  of  offense  and  defense;  fourth,  protec- 
tion and  concealment  by  methods  of  burrowing.^ 

There  are  heavy  protective  coverings  for  slowly  moving 
and  sessile  animals.  In  contrast  we  find  swiftly  moving  types 
(e.  g.,  Sagitta  and  other  cha^tognaths)  with  the  lines  of  modern 
submarines,  whose  mechanical  means  of  propulsion  resemble 
those  of  the  most  primitive  darting  fishes.  Other  types,  such 
as  the  Crustacea,  have  skeletal  parts  for  the  triple  purposes  of 
defense,  offense,  and  locomotion,  some  being  adapted  to  less 
swift  motion.  In  Palaeozoic  time  they  include  the  slowly 
moving,  bottom-living,  armored  t>T>es  of  trilobites.  Then 
there  are  other  slowly  moving,  bottom-living  forms,  such  as 
the  brachiopods  and  gastropods,  with  very  dense  armature  of 
phosphate  and  carbonate  of  lime.  Finally,  there  are  pelagic 
or  surface-floating  types,  such  as  the  jellyfishes,  which  are 
chemically   protected    by    the    poisonous    secretions    of    their 

'^sting-cells.^' 

This  highly  varied  life  of  mid-Cambrian  time  affords  abun- 
dant evidence  that  in  pre-Cambrian  time  certain  of  the  inver- 
tebrates had  already  passed  through  first,  second,  and  even 
third  phases  of  form  in  adaptation  to  as  many  different  life 

zones. 

Our  first  actual  knowledge  of  such  extremely  ancient  adap- 

^  tations  dates  back  to  the  pre-Cambrian  and  is  afforded  by  Wal- 

cott's  discovery-  in  the  Greyson  shales  of  the  Algonkian  Belt 

1  R.  W.  Miner.  *  Walcott,  Charles  D.,  1899,  pp.  235-244. 


1 


•' 


CAMBRIAN  INVERTEBRATES 


121 


TRi  LOBITA 


•i ;.. 


'  :'/'  ■rli^ 


Series  of  fragmentary  remains  of  that  problematic  fossil,  Bel- 
Una  danai,  which  he  refers  to  the  Merostomata  and  near  to  the 
eurypterids,  thus  making  it  probable  that  either  eurypterids,  or 
forms  ancestral  both  to  trilobites  and  eurypterids  existed  in  pre- 
Cambrian  times.    More  extensive  adaptive  radiations  are  found 
in  the  Lower  Cambrian  life  period  of  Olenellus,     This  trilobite 
is  not  primitive  but  a  compound  phase  of  evolution,  and  rep- 
resents the  highest  trilobite 
development.      Trilobites 
are  beautifully  preserved  as 
fossils  because  of  their  dense 
chitinous  armature,   which 
protected  them  and  at  the 
same  time  admitted  of  con- 
siderable   freedom   of    mo- 
tion.    The  relationships  of 
the   trilobites  to  other  in- 
vertebrates have  long  been 
in    dispute,    but    the    dis- 
covery of  the  ventral  sur- 
face and  appendages  in  the  mid-Cambrian  Neolenus  serratus 
(Fig.  20)  seems  to  place  the  trilobites  definitely  as  a  subclass 
of  the  Crustacea,  with  affinities  to  the  freely  swimming  phyl- 
lopods,  which  swarm  on  the  surface  of  the  existing  oceans. 

A  most  significant  biological  fact  is  that  certain  of  the^' 
primitively  armored  and  sessile  brachiopods  of  the  Cambrian 
seas  have  remained  almost  unchanged  generically  for  a  period^ 
of  nearly  thirty  million  years,  down  to  the  present  time.  These 
animals  afford  a  classic  illustration  of  the  rather  exceptional 
condition  known  to  evolutionists  as  ^^ balance,''  resulting  in 
absolute  stability  of  type.  One  example  is  found  in  Lingulella 
{Lingiila),  of  which  the  fossil  form,  Lingulella  acuminata,  char- 


N  »  r; .;  g  ^ 


S  #  '  r  *  t  L  - 


Fig.  20.    A  Mid-Cambrian  Trilobite. 
Neolenus  serratus  (Rominger) .    After  Walcott. 


'\ 


122 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


acteristic  of  Cambrian  and  Ordovician  times,  is  closely  similar 
to  that  of  Lingula  anatina,  a  species  living  to-day.  Represen- 
tatives of  the  genus  Lingula  {Lingulella)  have  persisted  from 
Cambrian  to  Recent  times.  The  great  antiquity  of  the  brachi- 
opods  as  a  group  is  well  illustrated  by  the  persistence  of  Lingula 
(Cambrian— Ordovician— Recent),  on  the  one  hand,  and  of 
Terebratula  (Devonian— Recent),  belonging  to  a  widely  differ- 
ing family,  on  the  other.  These  lamp-shells  are  thus  charac- 
teristic of  all  geologic  ages,  including  the  present.  Reaching 
their  maximum  radiation  during  the  Ordovician  and  Silurian, 
they  gradually  lost  their  importance  during  the  Devonian  and 
Permian,  and  at  the  present  time  have  dwindled  into  a  rela- 
tively insignificant  group,  members  of  which  range  from  the 
oceanic  shore-line  to  the  deep-sea  or  abyssal  habitat. 

By  the  Middle  Cambrian  the  continental  seas  covered  the 
whole  region  of  the  present  Cordilleras  of  the  Pacific  coast. 
In  the  present  region  of  Mount  Stephen,  B.  C,  in  the  unusually 
favorable  marine  oily  shales  of  the  Burgess  formation,  the 
remarkable  evolution  of  invertebrate  life  prior  to  Cambrian 
time  has  been  revealed  through  Walcott's  epoch-making  dis- 
coveries between  1909  and  191 2. ^  It  is  at  once  evident  (Figs. 
20-27)  that  the  seashore  and  pelagic  life  of  this  time  exhibits 
types  as  widely  divergent  as  those  which  now  occur  among 
the  aquatic  Invertebrata;  in  other  words,  the  extremes  of 
invertebrate  evolution  in  the  seas  were  reached  some  thirty 
million  years  ago.  Not  only  are  the  characteristic  external 
features  of  these  soft-bodied  invertebrates  evident  in  the  fossil 
remains,  but  in  some  cases  (Fig.  22)  even  the  internal  organs 
show  through  the  imprint  of  the  transparent  integument. 
Walcott's  researches  on  this  superb  series  have  brought  out 
two  important  points:  First,  the  great  antiquity  of  the  chief 

1  Walcott,  Charles  I).,  191 1,  1912. 


CAMBRIAN   INVERTEBRATES 


123 


aquatic  invertebrate  groups  and  their  high  degree  of  special- 
ization in  Early  Cambrian  times,  which  makes  it  necessary  to 
look  for  their  origin  far  back  in  the  pre-Cambrian  ages;  and, 
second,  the  extraordinary  persistence  of  type,  not  only  among 
the  lamp-shells  (brachiopods)  but  among  members  of  all  the 
invertebrate    phyla   from   the   mid-Cambrian   to   the   present 


BRACHIOPODA 


B  R  A  C  H  1  O  P  O  D  ^ 


.ln9ul«H»(Fo»«i< 
C»r«brian-Htc«rtl 


I  n  gw  I  e  >  •  i»  iJE 

Camb-Recent  ■ 


Devon  -Recent    \ 


Fig.  21.    Brachiopods,  Cambrian  and  Recent. 

Limidella  {Lingula)  acumhiata,  a  fossil  form  ranging  from  Cambrian  to  Ordovician, 
and  tt  very  similar  existing  form,  Ling:da  anatina,  which  shows  that  the  genus  has 
persisted  from  Cambrian  times  down  to  the  present  day.  ^ 

LLuldla  (fossil),  Cambrian  to  Ordovician,  contrasted  with  a  livmg  specimen  of  the 
widely  differing  Terebratula,  which  ranges  from  Devonian  to  recent  times. 

time,  so  that  sea  forms  with  an  antiquity  estimated  at  twenty- 
five  million  years  can  be  placed  side  by  side  with  existing  sea 
forms  with  very  obvious  similarities  of  function  and  structure, 
as  in  the  series  arranged  for  these  lectures  by  Mr.  Roy  W. 
Miner,  of  the  American  Museum  of  Natural  History  (Figs.  21, 

22,  24-27). 

Except  for   the   trilobites,   the  existence  of  Crustacea  in 
Cambrian  times  was  unknown  until  the  discovery  of  the  prim- 


124 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


CAMBRIAN  INVERTEBRATES 


125 


itive  shrimp-like  form,  Burgessia  hella  (Fig.  22),  a  true  crusta- 
cean, which  may  be  compared  with  Apus  lucasanus,  a  mem- 
ber of  the  most  nearly  alHed  recent  group.  We  observe  a 
close  correspondence  in  the  shape  of  the  chitinous  shield  (car- 
apace), in  the  arrangement  of  the  leaf-like  locomotor  appen- 
dages at  the  base  of  the  tail,  and  in  the  clear  internal  impres- 


FiG.  2  2.    Horseshoe  Crab  and  Shrimp,  Cambrian  and  Recent. 

Molaria    spinifcra,   a   mid-Cambrian   merostome    (after  Walcott),  compared  with   the 

recent  "horseshoe  crab,"  Limuliis  polyphcmiis. 
Burgessia   bclla,  a   shrimp-like  crustacean   of   the   Middle   Cambrian    (after    Walcott), 

compared  with  the  very  similar  Apus  lucasanus  of  recent  times. 

sions  in  Burgessia  of  the  so-called  ^'kidneys,''  with  their 
branched  tubules.  The  position  of  these  organs  in  Apus  is 
indicated  by  the  two  light  areas  on  the  carapace.  Other 
specimens  of  Burgessia  found  by  Walcott  show  that  the  taper- 
ing abdominal  region  and  tail  are  jointed  as  in  Apus, 

The  age  of  the  armored  merostome  arthropods  is  also 
thrust  back  to  mid-Cambrian  times  by  the  discovery  of  several 
genera  of  Aglaspidae,  the  typical  species  of  which,  Molaria 
spinifera  Walcott,  may  be  compared  with  that  ''Hving  fossil," 


the  horseshoe  crab  {Limulus  polyphemus),  its  nearest  modern 
relative,  which  is  believed  to  be  not  so  closely  related  to  the 
phyllopod  crustaceans  as  would  at  first  appear,  but  rather  to 
the  Arachnida  through  the  eur>T)terids  and  scorpions.  Mo- 
laria and  Limulus  are  strikingly  similar  in  their  cephalic  shield. 


CAMBRIAN 


PALCOGEOGRAPHY.  MIDDLE  CAMBBIAN  (ACADIAN  OR  PARADOXIDESI  TIME 
AFTER  SCHOCMEBT,  APRIL.  1»H 


^  MARINE  DEPOSITS 


Fig.  23.    Theoretic  World  Environment  in  Middle  Cambrian  Time. 

The  period  of  the  trilobite  Paradoxidcs.     This  shows  the  theoretic  South  Atlantic  con- 
tinent "Gondwana"  of  Suess,  connecting  Africa  and  South  America. 

segmentation,  and  telson;  but  the  latter  shows  an  advance 
upon  the  earlier  type  in  the  coalescence  of  the  abdominal  seg- 
ments into  a  single  abdominal  shield-plate.  The  trilobate 
character  of  the  cephalic  shield  in  Molaria  is  an  indication  of 
its  trilobite  affinities;  hence  we  apparently  have  good  reason 
to  refer  both  the  merostomes  and  phyllopods  to  an  ancestral 

trilobite  stock. 

Another   mode   of   defense   is   presented    by   some    of   the 
sessile,  rock-clinging  sea-cucumbers  (Holothuroidea)  protected 


u 


126 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


not  only  by  their  habit  of  hiding  in  crevices,  but  by  their 
leathery  epidermis,  in  which  are  scattered  a  number  of  cal- 
careous plates,  as  among  certain  members  of  the  modern  eden- 
tate mammals.  Fossils  of  this  group  have  been  known  here- 
tofore only  through  scattered  spicules  and  calcareous  plates 
dating  back  no  earlier  than  Carboniferous  times  (Goodrich); 
therefore  Walcott's  holothurian  material  from  the  Cambrian 
constitutes  new  records  for  invertebrate  palaeontology,  not 
only  for  the  preservation  of  the  soft  parts,  but  for  the  great 
antiquity  of  these  Cambrian  strata.  In  Louisella  pedunculata 
(Fig.  24)  we  observe  the  preservation  of  a  double  row  of  tube- 
feet,  and  the  indication  at  the  top  of  oral  tentacles  around  the 
mouth  like  those  of  the  modern  Elpidiidae.  A  typical  rock- 
clinging  holothurian  is  the  recent  Pentada  frondosa. 

Besides  these  sessile,  rock-clinging  forms,  the  adaptive 
radiation  of  the  holothurians  developed  burrowing  or  fossorial 
types,  an  example  of  which  is  the  mid-Cambrian  Mackenzia 
costalis  (Fig.  24)  which  strikingly  suggests  one  of  the  existing 
burrowing  sea-cucumbers,  Synapta  girardii.  The  character- 
istic elongated  cylindrical  body-form  with  longitudinal  muscle- 
bands  is  clearly  preserved  in  the  fossil,  while  around  the  mouth 
is  a  ring  of  tubercles  interpreted  by  Walcott  as  calcareous 
ossicles  from  above  which  the  oral  tentacles  have  been  torn 
away. 

A  remarkable  and  problematic  mid-Cambrian  fossil,  Eldonia 
liidwigi  (Fig.  24),  is  regarded  by  Walcott  as  a  free-swimming 
or  pelagic  animal.  It  bears  a  superficial  resemblance  to  a 
medusa,  or  jellyfish,  while  the  lines  radiating  from  a  central 
ring  suggest  the  existence  of  a  water  vascular  system;  but  the 
cylindrical  body  coiled  around  the  centre  shows  a  spiral  intes- 
tine through  its  transparent  body-wall,  and  it  is  therefore  con- 
sidered to  be  a  swimming  holothurian,  or  sea-cucumber,  with 


CAMBRIAN  INVERTEBRATES 


127 


a  medusa-like  umbrella.     The  existing  holothuroid  Pelagothiiria 
natatrix  Ludwig,  shown  at  the  right,  is  somewhat  analogous, 


Fig.  24.    Sea-Cucumbers  of  Cambrian  and  Recent  Seas. 

FMonia  hidwigioi  the  mid-Cambrian  (after  Walcott),  regarded  as  pelagic  and  somewhat 
resembling  a  jellyfish,  is  thought  rather  to  be  a  form  analogous  to  Pelagothiiria  nata- 
trix, a  swimming  sea-cucumber,  although  it  shows  wide  differences.  The  mouth  of 
Pelagothiiria  is  above  the  swimming  umbrella,  the  posterior  part  of  the  body  and  the 
anal^opcning  are  below:    in  the  fossil  Eldonia  both  mouth  and  anus  hang  below. 

Mackenzia  costalis,  a  mid-Cambrian  form  (after  Walcott),  strongly  resembling  the  bur- 
rowing sea-cucumbers,  a  recent  form  of  which,  Synapta  girardii,  is  shown  at  the  right. 
LouiscUa  pedunculata,  another  mid-Cambrian  form  (after  Walcott),  and  a  recent 
rock-clinging  form,  Pentacta  frondosa. 

although   it   also   displays   wide   differences   of   structure.     If 
Eldonia  ludwigi  proves  to  be  a  holothurian,  we  witness  in  mid- 


128 


THE  ORIGIN  AND   EVOLUTION  OF   LIFE 


Cambrian  strata  members  of  this  order  differentiated  into  at 
least  three  widely  distinct  families. 

The  worms,  including  swimming  and  burrowing  annulates, 

are  represented  in  the  Bur- 
gess fauna  by  a  very  large 
number  of  specimens,  com- 
prising nineteen  species,  dis- 
tributed  through  eleven 
genera    and    six     families. 
Most  of   these   are   of  the 
order  Polycha^ta,  as,  for  ex- 
ample, Worthenella  Cambria^ 
in  which  the  head  is  armed 
with    tentacles,    while    the 
segmented    body    and    the 
continuous  series  of  bilobed 
parapodia   are    very   clear. 
When  compared  with  such 
typical  living  polycha^tes  as 
Nereis  virens   and  Arabella 
opalina  (Fig.  25),  we  have 
clear  proof  of  the  modern 
relationships  of  these  mid- 
Cambrian  species,  as  well  as 
of  Cambrian  sea-shore  and 
tidal  conditions  closely 
similar  to  those  of  the  pres- 
ent time.     A  specialization 
toward  the  spiny  or  scaly 
annulates  at  this  period  is 
emphasized  in  such  forms  as  Canadia  spinosa  (Fig.  25),  a  slowly 
moving  form  which  shows  a  development  of  lateral  chcTtae  and 


CAMBRIAN  INVERTEBRATES 


129 


Fig.  25.    Worms  (.\nnulata)  of  the  Middle 
Cambrian  and  Recent  Seashores. 

Canadia  spinosa,  a  mid- Cambrian  form  (after 
Walcott)  with  overlapping  groups  of  scale- 
like dorsal  spines,  resembling  those  of  the  liv- 
ing AphroditidcE:,  such  as  Polyno'6  sqiiamata. 

Worthenella  cambria,  a  worm  of  mid-Cambrian 
times  (after  Walcott) ,  compared  with  Nereis 
virens  and  Arabella  opalina,  recent  marine 
worms. 


CH/ETOGNATHA 


overlapping  groups  of  scale-like  dorsal  spines  comparable  only 
to  those  of  the  living  Aphroditidae.  An  example  of  this  latter 
family  is  Polynoe  squamata,  furnished  with  dorsal  scales.  Still 
other  recent  forms,  such  as  Palmyra  aurifera  Savigny,  have 
groups  of  spinous  scales  closely 
resembling  those  of  Canadia, 

Even  the  modern  freely  pro- 
pelled Chcrtognatha  have  their 
representatives  in  the  mid- 
Cambrian,  for  to  no  other  group 
of  invertebrates  can  Amiskwia 
sagittiformis  Walcott  (Fig.  26) 
be  referred,  so  far  as  we  can 
judge  by  its  external  form.  As 
in  the  recent  Sagitta  the  body 
is  divided  into  head,  trunk,  and 
a  somewhat  fish-like  tail.  Its 
single  pair  of  fins  of  chaetognath 
type  would  perhaps  give  a 
clearer  affinity  to  the  genus 
Spadella.  The  conspicuous  pair 
of  tentacles  which  surmounts 
the  head  is  absent  in  modern 

cha^tognaths,  although  some  recent  species  show  a  pair  of  sen- 
sory papillae  mounted  on  a  stalk  on  either  side  of  the  head,  as 
in  Spadella  cephaloptera  Bush.  The  digestive  canal  and  other 
digestive  organs  appear  through  the  thin  walls  of  the  body. 

A  modern  group  of  jellyfishes,  the  Scyphomedusae  (Fig.  27), 
is  represented  by  the  Middle  Cambrian  Peytoia  nathorsti,  the 
elliptical  disk  of  which  is  seen  from  below.  Although  this 
fossil  species  is  ascribed  by  Walcott  to  the  group  Rhizostomae 
because  of  a  lack  of  marginal  tentacles,  the  thirty-two  radiat- 


L 


Amiskwia 

Mid   Cambrian 


Sagitta 

Recent 


Fig.  26.    Freely  Swimming  CniETOG- 
NATHS,  Cambrian  and  Recent. 

Amiskwia  sagittiformis,  a  mid-Cambrian 
form  (after  Walcott),  has  a  body  di- 
vided into  head,  trunk,  and  tail  like  the 
recent  Sagitta,  as  seen  in  S.  gar  diner  i. 


I30 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


ing  lobes  which  are  so  beautifully  preserved  in  the  fossil  cor. 
respond  closely  with  those  of  the  existing  genus  Dactylomdra 
of  the  suborder  Semostomai.     It  is  possible  that  the  marginal 
tentacles  may  have  been  lost  in  Peytoia,  as  so  frequently  hap- 
pens in  Hving  jellyfishes  when  in  a  dying  condition. 

From  the  Burgess  fauna  it  appears  that  the  pre-Cambrian 
invertebrates  had  entered  and  become  completely  adapted  to 

all  the  life  zones  of  the 
continental  and  oceanic 
waters,  except  possibly 
the  abyssal.  All  the 
principal  phyla — the 
segmented  Annulata, 
the  jointed  Arthropoda 
(including  trilobites, 
merostomes,  crusta- 
ceans, arachnids,  and 
insects),  medusae  and 
other  coelenterates, 
echinoderms,  brachio- 
pods,  molluscs  (includ- 
ing pelycypods,  gastro- 


FiG.  27.    Jellyfish,  Cambrian  and  Recent. 

Peytoia  nathorsli,  mid-Cambrian  (after  Walcott), 
and  Dadylomctra  quinquecirra,  recent.  The 
thirty-two  lobes  of  the  fossil  specimen  corre- 
spond with  the  same  number  often  observed  in 
Dactylometra,  and  the  characteristic  marginal 
tentacles  may  have  been  lost  in  Peytoia, 


pods,  ammonites,  and  other  cephalopods),  and  sponges— were  all 
clearly  established  in  pre-Cambrian  times.  Which  one  of  these 
great  invertebrate  divisions  gave  rise  to  the  vertebrates  remains 
to  be  determined  by  future  discovery.  At  present  the  Annulata, 
Arthropoda,  and  Echinodermata  all  have  their  advocates  as 
being  theoretically  related  to  the  ancestors  of  the  vertebrates. 
The  evolution  of  each  of  these  invertebrate  types  follows  the 
laws  of  adaptive  radiation,  and  in  the  case  of  the  articulates  and 
molluscs  extends  into  the  terrestrial  and  arboreal  habitat  zones, 
while  many  branches  of  the  articulates  enter  the  aerial  zone. 


•. 


EVOLUTION  OF  DtVERGENT  AND  ANALOGOUS  MODES  OF  RESPIRATION,  MOTION.  FEEDING,  OFFENSE  AND  DEFENSE. 


AERIAL 
A^RS  ARBOR!: 


^ 


ARBOREAL 


ARB0R2TERRI 


TERRESTRIAL 
TERRfi  FOSSORt 


FOSSORIAL 
TERR2  AQUATIC 


AQUATJCFLUVt? 


♦» 


LITTORAL 


"     PELAGIC 
"    ABYSSAL 


.0- 


o 


S3 

z 
-o- 

m 


law  of  adaptive  radiation 
Fig.  28.    The  Twel\e  Chief  Habitat  Zones  of  Animal  Life. 

These  twelve  zones  compose  the  environment,  aerial  to  abyssal,  into  which  the  Inver- 
tebrata  and  Vertebrata  have  adaptively  radiated  in  the  course  of  geologic  time.  The 
Invertebrates  range  from  the  abyssal  to  the  aerial  zones.  The  fishes,  ranging  only 
from  the  terrestrio-aquatic  to  the  abyssal  habitat  zones,  nevertheless  evolve  body 
forms  and  types  of  locomotion  similar  to  those  observed  in  the  Amphibia,  which  range 
from  the  littoral  to  the  arboreal  habitat  zones.  The  reptiles,  birds,  and  mammals, 
ranging  from  the  aerial  to  the  pelagic  habitat  zones,  independently  evolve  through 
the  law  of  adaptive  radiation  many  convergent,  parallel,  or  similar  types  of  body 
form,  as  well  as  similar  modes  of  locomotion  and  of  offense  and  defense. 


Fig.  29.    Life  Zones  of  Cambrian  and  Recent  Im^RTEBRATES. 

Chart  showing  in  shaded  areas  the  limited  habitat  zones— Littoral,  Pelagic,  Abyssal— of 
the  known  Cambrian  forms  (left)  compared  with  the  wide  adaptive  radiation  (Abyssal 
to  Arboreal)  of  recent  forms  (right).     By  Roy  \V.  Miner. 

131 


132 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


The  evolution  of  the  articulates^  is  believed  to  be  as  follows: 
From  a  pre-Cambrian  annelidan  (worm-like)  stock  arose  the 
trilobites  with  their  chitinous  armature  and  many-jointed 
bodies.     The  same  stock  gave  rise  also  to  the  chitin-armored 


Fig.  30.    Environment.    North  America  in  Cambrian  Times. 

Theoretic  restoration  of  the  North  American  continent  (white),  continental  seas  (gray), 
and  ocean  (dark  gray)  in  Upper  Cambrian  (Lower  Saint-Croixian)  time,  during  which 
there  occurred  the  earliest  known  great  invasion  of  land  by  the  oceans.  This  period 
marks  the  rise  of  invertebrate  gastropods,  limulids,  eur>'pterids,  and  articulate  brach- 
iopods,  and  the  greatest  differentiation  of  trilobites.  The  lands  were  probably  all 
low  and  the  climate  warm.  Detail  from  the  globe  model  in  the  American  Museum 
by  Chester  A.  Reeds  and  George  Robertson,  after  Schuchert. 

sea-scorpions,  or  eur^T^terids,  which  attained  a  great  size  and 
dominated  the  seas  of  Silurian  times  (Fig.  31).  Another  line 
from  the  same  stock  is  that  of  the  chitin-armored  horseshoe 
crab  (Limulus),  Out  of  the  eur>T>terid  stock  of  Silurian  times 
may  have  come  the  terrestrial  scorpions,  fossils  of  which  are 

1  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  191 5,  P-  608. 


CAMBRIAN  INVERTEBRATES 


^33 


first  known  in  the  Silurian,  and  through  it  arose  the  entire 
group  of  arachnoid  (spider-like)  animals,  including  the  existing 
scorpions,   spiders,   and   mites.     It   is   also  possible   that   the 


Fig.  31.    EuRYPTERiDS  OR  Sea-Scorpions  of  Silurian  Times. 

A.  Restoration  of  the  giant  eurypterid,  Styloniirus  excelsior,  from  the  Catskill  sandstone. 

Natural  length,  four  feet. 

B.  Restoration  of  pMsarcus,  from  the  Bertie  water-lime.     Natural  length,  three  feet. 

C.  Restoration  of  Eusarcus,  age  of  the  Bertie  water-lime.     (After  John  M.  Clarke.) 

amphibious,  terrestrial,  and  aerial  Insecta  were  derived  from 
some  Silurian  or  Devonian  chitin-armored  articulate.  The 
true  Crustacea  also  have  probably  developed  out  of  the  same 


134  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

pre-Cambrian  stock,  giving  rise  to  the  phyllopods  and  other 
true  Crustacea  of  the  Cambrian,  and  to  the  cirripedes  or  bar- 
nacles of  the  Ordovician. 


Fig.  32.    North  America  in  Middle  Devonian  Times. 

Theoretic  restoration  of  the  North  American  continent  (white),  continental  seas  (gray), 
and  ocean  (dark  gray),  in  Middle  Devonian  (Hamilton)  time,  fhis  period  is 
marked  by  the  last  extensive  inundation  of  the  Arctic  seas  by  the  rise  of  the  Schick- 
chockian  ISIountains  and  many  volcanoes  in  Acadia,  and  by  the  beginning  of  the 
great  CatskiU  delta  built  up  by  rivers  from  the  rising  Acadian  region.  Marine  shark 
and  arthrodires  become  abundant,  the  American  fauna  of  the  Mississippi  Sea  shows 
numerous  brachiopods  and  bivalves,  and  the  first  evidence  of  a  land  flora  with  large 
conifers  {Dadoxvlon)  is  found.  Detail  from  a  globe  model  in  the  American  ]Museum 
by  Chester  A.  Reeds  and  George  Robertson,  after  Schuchert. 

Reactions  to  Climatic  and  Other  Environmental 

Changes  of  Geologic  Time 

Schuchert  observes  that  there  is  no  more  significant  period 
in  the  history  of  the  world  than  the  Devonian^  (Fig.  32),  for 
at  this  time  the  increasing  verdure  of  the  land  invited  the 

1  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  1915,  P-  7U. 


tn    cS    O 


\ 


135 


/ 


) 


136 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


invasion  of  life  from  the  waters,  the  first  conquest  of  the  terres- 
trial environment  being  attained  by  the  scorpions,  shell-fish, 
worms,  and  insects. 

This  is  an  instance  of  the  constant  dispersion  of  animal 
forms  into  new  environments  in  search  of  their  food-supply, 

the  chief  instinctive 
cause  of  all  migration. 
This  impulse  is  con- 
stantly acting  and  react- 
ing throughout  geologic 
time  with  the  migration 
of  the  environment, 
which  is  graphically  pre- 
sented by  Huntington's 
chart  (Fig.  ;^2,),  from  the 
researches  of  Barrell, 
Schuchert,  and  others. 
The  periodic  readjust- 
ment of  the  earth  crust 
of  North  America^  is 
witnessed  in  fourteen 
periods  of  mountain- 
making  (oblique  lines), 
concluding  with  the  Appalachian  Range,  the  Sierra  Nevada 
(Sierran),  the  Rocky  Mountains  (Laramide),  and  the  Pacific 
Coast  Range. 

Between  these  relatively  short  periods  of  mountain  up- 
heaval came-  periods  of  continental  depression  and  oceanic 
invasion  (horizontal  lines)  when  the  continent  was  more  or 
less  flooded  by  the  oceans.  There  are  certainly  twelve  and 
probably  not  less  than  seventeen  periods  of  continental  flood- 

1  Pirsson,  Louis  V.,  and  Schuchert,  Charles,  1915,  p.  979.  '  Op,  cil.,  p.  982. 


Fig.  34.    Fossil  Starfishes. 

A  portion  of  petrified  sea  bottom  of  Devonian  age, 
showing  fossil  starfishes  associated  with  and 
devouring  bivalves  as  starfishes  attack  oyster- 
beds  at  the  present  time.  Hamilton  group, 
Saugerties,  N.  Y.     After  John  M.  Clarke. 


} 


\ 


ENVIRONMENTAL  CHANGES 


137 


ing  which  vary  in  extent  up  to  the  submergence  of  4,000,000 

square  miles  of  surface. 

Each  of  these  changes,  which  by  some  geologists  are  be- 
lieved to  be  cyclic,  included  long  epochs  especially  favorable 
to  certain  forms  of  life,  resulting  in  the  majority  of  cases  in 
high  specialization  like  that  of  the  sea-scorpions  (eurypterids) 
followed  by  more  or  less  sudden  extinction.  In  the  oceans  the 
life  most  directly  influenced  was  that  of  the  Ume-secreting 
organisms  which  resulted  in  maximum  and  minimum  periods 
of  limestone  formation  (oblique  Unes)  by  algae,  pelagic  fora- 
minifera,  and  corals.  On  land  there  were  two  greater  (Car- 
boniferous, Upper  Cretaceous)   and  several  lesser  periods  of 

coal  formation. 

Changes  of  environment  play  so  large  and  conspicuous  a 
part  in  the  selection  and  elimination  of  the  invertebrates  that 
the  assertion  is  often  made  that  environment  is  the  cause  of 
evolution,  a  statement  only  partly  consistent  with  our  funda- 
mental biologic  law,  which  finds  that  the  causes  of  evolution 
lie  within  the  four  complexes  of  action,  reaction,  and  inter- 
action (see  p.  21). 

Perrin  Smith,  who  has  made  a  most  exhaustive  analysis  of 
the  evolution  of  the  cephalopod  molluscs  and  especially  of 
the  Triassic  ammonites,  observes  that  the  evolution  of  form 
continues  uninterruptedly,  even  where  there  is  no  evidence 
whatever  of  environmental  change.  Conversely,  environmen- 
tal change  does  not  necessarily  induce  evolution— for  exam- 
ple, during  the  Age  of  Mammals,  although  the  mammals  de- 
veloped an  infinite  variety  of  widely  divergent  forms,  the  rep- 
tiles (p.  231)  show  very  little  change. 


1 


138 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


The  Mutations  of  Waagen 


When  Darwin  published  the  ''Origin  of  Species/'  in  1859, 
no  one  had  actiially  observed  how  one  form  of  animal  or  plant 
actually  passes  into  another^  whether  according  to  some  definite 
law  or  principle,  or  whether  fortuitously  or  by  chance.  So 
far  as  we  know,  the  honor  of  first  observing  how  new  specific 
forms  arise  belongs  to  Wilhelm  Heinrich  Waagen.^  It  was 
among  the  fossil  ammonites  of  the  Jurassic,  which  are  repre- 
sented by  the  existing  pearly  nautilus,  that  Waagen  first  ob- 
served the  actual  mode  of  transformation  of  one  animal  form 
into  another,  as  set  forth  in  his  classic  paper  of  1869,  ''Die 
Formenreihe  des  Ammonites  subradiatus.'^^  The  essential  fea- 
ture of  the  "mutation  of  Waagen''^  is  that  it  established  the 
law  of  minute  and  inconspicuous  changes  of  form  which  ac- 
cumulate so  gradually  that  they  are  observable  only  after  a 
considerable  passage  of  time,  and  which  take  a  definite  direc- 
tion as  expressed  in  the  word  Mutationsrichtung.  We  now 
recognize  that  they  represent  a  true  evolution  of  the  heredity- 
chromatin.  This  law  of  definitely  directed  evolution  is  illus- 
trated in  the  detailed  structure  of  the  t>^e  series  of  ammon- 
ites (Fig.  35)  in  which  Waagen's  discovery  was  made.  It  has 
proved  to  be  a  fundamental  law  of  the  evolution  of  form,  for 
it  is  observed  alike  in  invertebrates  and  vertebrates  wherever 
a  closely  successive  series  can  be  obtained. 

Among  the  fossil  invertebrates  a  mutation  series  of  the 
brachiopod,  Spirifer  mucronatus  of  the  Middle  Devonian  or 
Hamilton  time,  is  one  of  the  most  t>pical  (Fig.  36). 

The  essential  law  discovered  by  Waagen  is  one  of  the  most 

*  Bom  in  1841,  died  in  1900.     An  Austrian  palaeontologist  and  stratigraphic  geologist. 

2  Waagen,  Wilhelm,  1869. 

'  The  term  "  mutation  "  used  in  this  sense  was  introduced  by  Waagen  in  1869.  Twenty 
years  later  the  great  Austrian  palaeontologist  Neumayr  defined  the  "Mutationsrichtung" 
as  the  tendency  of  form  to  evolve  in  certain  definite  directions.  See  Neumayr,  M.,  1889, 
pp.  6oj  61. 


MUTATIONS  OF  WAAGEN 


139 


important  in  the  whole  history  of  biology.  It  is  that  certain 
new  characters  arise  definitely  and  continuously,  and,  as 
Osborn  has  subsequently  shown, ^  adaptively.     This  law  of  the 


Zone  des 
A.  MACROCEPHALUS 


Zone  des 
A.  ASPIDOIDES 


Zone  der 
TERDIGONA 


Zone  des 

A.  FERRUGINEUS 


Zone  des 
A.  PARKINSONI 


ZoMiles 
A.  HUMPHRIESIANUS 


A.  MAMERTENSIS 


A.  SUBCOSTARIUS 


A.  SUBOISCUS 


A.  ASPIDOIDES 


A.  LATILOBATUS 


A,  BIFLEXUOSUS 


A.  FUSCUS 


A.  SUBRADIATO^ 


COLLECTIVART-    A.  SUBRADIATUS 

Fig.  35.    Continuous  Character  Changes  Known  as  the  Mutations  of  Waagen. 

Successive  geologic  mutations  of  Ammonites  subradiatus,  drawn  and  rearranged  from  the 
original  plates  published  by  Waagen  in  1869,  showing  his  type  series  of  the  contin- 
uous character  changes  known  as  the  Mutations  of  Waagen. 

1  Osborn,  Henry  Fairfield,  1912.1. 


I40 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


gradual  evolution  of  adaptive  form  is  directly  contrary  to 
Darwin's  theoretic  principle  of  the  selection  of  chance  varia- 
tions. It  is  unfortunate  that  the  same  term,  mutation,  was 
chosen  by  the  botanist,  Hugo  de  Vries,  in  1901,  to  express  his 
observation  that  certain  characters  in  plants  arise  by  sudden 


THCoronoCNSC 


WWFUNOUS 


AftCNUATUS 


MUtTlPLICATUS 


•mm-^  (I  ) 


I 


\  ^-. 


I 


AMTMM  H>CH  aHAiX 


(1-**) 


-^„.. 


Z7 


ALPCNCNSe 


PAirrCQC  PT  KM 


porrtnrnmt 


•LPCN«UMC9T0NC 


90MMCMVILU  UMUTQNK 
CLCAJONOAy 


MKIOLC  Ura  IMALt 


(177) 
COLLECTIVART-SPIRIFER  MUCRONATUS 

Fig.  36.    Successive:  Mutations  of  Spirifcr  mucronalns. 

Specimens  from  the  geologic  section  at  Alpena,  Mich.,  on  the  shore  of  Lake  Huron, 
and  from  the  corresponding  section  at  Thedford  across  the  lake  on  the  Canadian 
shore,  arranged  by  A.  Grabau  to  show  the  relationships  of  the  various  mutations. 
In  the  scale  of  strata  at  the  right  ^%  mm.  equals  loo  feet  depth. 

changes  (saltations)  or  discontinuously,  and  without  any  defi- 
nite direction  or  adaptive  trend  (Mutationsrichtiing).  The 
essential  feature  of  de  Vries's  observations,  in  contrast  to 
Waagen's,  is  that  of  discontinuous  saltations  in  directions  that 
are  entirely  fortuitous— that  is,  either  in  an  adaptive  or  in- 
adaptive  direction,  the  direction  to  be  subsequently  deter- 
mined by  selection— a  theoretic  principle  agreeing  closely  with 
that  of  Darwin. 


CHAPTER  V 

VISIBLE  AND  INVISIBLE  EVOLUTION  OF  THE 

VERTEBRATES 

Chromatin  evolution.  Errors  and  truths  in  the  Lamarckian  and  Darwinian 
explanations  of  the  processes  of  evolution.  Character  evolution  more 
important  than  species  evolution.  Individuality  in  character  origin, 
velocity,  and  cooperation.  Origin  of  the  vertebrate  type.  The  laws 
of  convergence,  divergence,  and  adaptive  radiation  of  form. 

Simon  Newcomb^  considered  the  concept  of  the  rapid 
movement  of  the  solar  system  toward  Lyra  as  the  greatest 
which  has  ever  entered  the  human  mind.  He  remarks:  ^^If  I 
were  asked  what  is  the  greatest  fact  that  the  intellect  of  man 
has  ever  brought  to  light,  I  should  say  it  was  this:  Through  all 
human  history,  nay,  so  far  as  we  can  discover,  from  the  infancy 
of  time,  our  solar  system — sun,  planets,  and  moons — has  been 
flying  through  space  toward  the  constellation  Lyra  with  a 
speed  of  which  we  have  no  example  on  earth.  To  form  a  con- 
ception of  this  fact  the  reader  has  only  to  look  at  the  beauti- 
ful Lyra  and  reflect  that  for  every  second  that  the  clock  tells 
off  we  are  ten  miles  nearer  to  that  constellation. '' 

The  history  of  the  back-boned  animals  (Vertebrata)  as  the 
visible  expression  of  the  invisible  evolution  of  the  microscopic 
chromatin  presents  an  equally  great  concept  of  the  potential- 
ities of  matter  in  the  infinitely  minute  state. 

According  to  this  concept  our  study  of  the  evolution  of 
the  back-boned  animals  at  once  resolves  itself  into  two  parallel 
lines  of  inquiry  and  speculation,  which  can  never  be  divorced 
and  are  always  to  be  followed  in  observation  and  inference: 

*  Newcomb,  Simon,  1902  (ed.  of  1904,  p.  325). 

141 


142 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


EVOLUTION  OF  THE   GERM 


l!i 


The  Visible  Body 

The  evolution  of  somatic  (/.  e., 
bodily)  form  and  function  as  ob- 
served in  anatomy,  embryology,  pa- 
laeontology, and  physiology.  The 
rise,  differentiation,  and  change  of 
function  in  bodily  characters. 


The  Invisible  Germ 

The  evolution  of  heredity- 
CHROMATiN  as  inferred  from  the  in- 
cessant visible  evolution  of  Form 
and  Function.  The  rise  and  decline 
of  potentialities,  predispositions,  and 
other  germinal  characters. 


143 


A  clear  distinction  exists  between  the  slow,  stable  heredity- 
chromatin,  or  germ  evolution,  and  the  unstable  body  cell  evolu- 
tion as  viewed  by  the  experimental  zoologist.  The  body  is  un- 
stable because  it  is  immediately  sensitive  to  all  variations  of 
environment,  growth,  and  habit,  while  the  chromatin  alters  very 
slowly.  The  peculiar  significance  of  heredity-chromatin,  when 
viewed  in  the  long  perspective  of  geologic  time,  is  its  stability 
in  combination  with  incessant  plasticity  and  adaptability  to 
varying  environmental  conditions  and  new  forms  of  bodily 
action.  Chromatin  is  far  more  stable  than  the  surface  of  the 
earth.  Throughout,  the  potentiality  of  constant  changes  of 
proportion,  gain  and  loss  of  characters,  genesis  of  new  charac- 
ters, there  is  always  preserved  a  large  part  of  the  history  of 
antecedent  form  and  function.  In  the  vertebrates  chromatin 
evolution  is  mirrored  in  the  many  continuous  series  of  forms 
which  have  been  discovered,  also  in  the  perfection  of  mechani- 
cal detail  in  organisms  of  titanic  size  and  inconceivable  com- 
plexity, like  the  dinosaurs  among  reptiles  and  the  whales  among 
mammals,  which  rank  with  the  Sequoia  among  plants. 

Adaptive  Characters  of  Internal-External  Action, 

Reaction,  Interaction 

Of  the  causes^  of  this  slow  but  wonderful  process  of  chroma- 
tin evolution  there  are  two  historic  explanations,  each  adum- 
brated in  the  Greek  period  of  inquiry. 

*  See  Preface,  p.  ix. 


The  older,  known  as  the  Lamarckian,^  expressed  in  modern 
terms,  is  that  the  causes  of  the  genesis  of  new  form  and  new  func- 
tion are  to  be  sought  in  the  body 
cells  {soma),  on  the  hypothesis 
that  cellular  actions,  reactions, 
and  interactions  with  each  other 
and  with  the  environment  are 
in  some  way  impressed  physico- 
chemically  upon  and  are  heri- 
table by  the  chromatin.  This 
idea  was  originally  suggested 
by  the  accurate  observation  of 
early  naturalists  and  anatomists 
that  bodily  function  not  only 
controls  and  perfects  form  but 
is  generally  adaptive  or  pur- 
posive in  its  efi"ects  upon  form. 
According  to  this  Lamarck- 
Spencer-Cope  explanation  a 
change  of  environment,  of 
habit,  and  of  function  should  al- 
ways be  antecedent  to  changes 
of  form  in  succeeding  genera- 
tions; moreover,  if  this  explana- 
tion were  the  true  one,  succes- 
sive changes  in  evolutionary 
series  would  be  like  growth, 
they  would  be  observed  to  fol- 
low the  direct  lines  of  individ- 
ual action,  reaction,  and  inter- 
action,  and   the   young   would 

^  Cj.  Preface,  pp.  xiii,  xiv. 


Adaptations  of  Environmental  Cor- 
relation: 

respiratory,  olfactory,  visual, 
auditory,  thermal,  gravity 
functions  and  organs 

coordinative  and  correlative  to 
variations  of  light,  heat,  hu- 
midity, aridity,  caused  by  mi- 
grations of  the  individual  or 
of  the  environment. 

Adaptations  of  Internal  Correlation: 
correlation  and  coordination  of 
the  internal  growth  and  func- 
tions through  internal  secre- 
tions, enzymes,  and  the  ner- 
vous system. 

Adaptations  of  Nutrition 

(i)  ON  inorganic  compounds. 

(2)  on  bacteria. 

(3)  on  protophyta,  alg^,  etc. 

(4)  on  protozoa. 

(5)  on   higher   plants,    herbivo- 

rous diet. 

(6)  on  higher  animals,  carnivo- 

rous diet. 

(7)  parasitic,  without  or  within 

plants  and  animals. 

Adaptations  of  Individual  Competi- 
tion AND  Selection: 

(a)  selection,  affecting  varia- 
tion, RECTIGRADATION,  MUTA- 
TION, ORIGIN,  AND  DEVELOP- 
MENT OF  SINGLE  CHARACTERS, 
PROPORTIONS,   ETC. 

(b)  affecting  all  REPRODUCrrVE 
ORGANS,  PRIMARY  AND  SEC- 
ONDARY. 

Adaptations  of  Racial  Competition 
AND  Selection, 

AFFECTING  CHIEFLY  ALL  MOTOR,  PRO- 
TECTIVE, OFFENSIVE,  ANT)  DEFEN- 
SIVE STRUCTURES  OF  THE  ENDO- 
AND  EXOSKELETON;  also  REPRO- 
DUCTION  RATE. 

The  peculiar   significance  of 

THE  HEREDITY-CHROMATIN  is  itS  Sta- 
bility in  combination  with  incessant 
plasticity  and  adaptability  to  vary- 
ing environmental  conditions  and 
new  forms  of  bodily  action. 


144 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


be   increasingly  similar   to  the  adults   of   antecedent  genera- 
tions, which  is  frequently  the  case  but  unfortunately  for  the 
Lamarckian  explanation  is  not  invariably  the  case.     In  many 
parts  of  the  skeleton  chromatin  development  and  degeneration 
so  obviously  follow  bodily  use  and  disuse  that  Cope  was  led  to 
propose  a  law  which  he  termed  hathmism  (growth  force)  and  to 
explain  the  energy  phenomena  of  use  and  disuse  in  the  body 
tissues  as  the  cause  of  the  appearance  of  corresponding  energy 
potentialities  in  the  chromatin.     In  other  words,  he  believed 
that  the  energy  of  development  or  of  degeneration  in  the  bodily 
parts  of  the  individual  is  inherited  by  corresponding  parts  in 
the  germ.     Similar  opinions  prevail  among  most  anatomists 
(e.  g.,  Cunningham)  and  among  many  palaeontologists  and  zo- 
ologists {e.  g.,  Semon). 

The  opposed  explanation,  the  pure  Darwinian,^  as  restated 
by  Weismann  and  de  Vries,  is  that  the  genesis  of  new  form  and 
function  is  to  be  sought  in  the  germ  cells  or  chromatin.     This  is 
based  upon  an  h>T>othesis  which  is  directly  anti-Lamarckian, 
that  the  actions,  reactions,  and  interactions  which  cause  cer- 
tain bodily  organs  to  originate,  to  develop,  or  to  degenerate, 
to  exhibit  momentum  or  inertia  in  development,  do  not  give 
rise  to  corresponding  sets  of  predispositions  in  the  chromatin, 
and  are  thus  not  heritable.     According  to  this  explanation, 
body  cell  changes  do  not  exert  any  corresponding  specific  in- 
fluence on  the  germ  cells.     All  predispositions  to  new  form  and 
function  not  only  begin  in  the  germ  cells  but  are  more  or  less 
lawless  or  experimental;  they  are  constantly  being  tested  or 
tried  out  by  bodily  experience,  habits,  and  functions.     Techni- 
cally stated,  they  are  "fortuitous''  or  chance  variations,  fol- 
lowed by  selection  of  the  fittest  variations,  and  thus  giving 
rise  to  adaptations.     Thus  Darwin's  disciple,  Poulton,  also  de 

*  Cf.  Preface,  p.  xiv. 


EVOLUTION  OF  THE  GERM 


145 


, 


Vries,  who  has  merely  restated  in  his  law  of  ''mutation"  Dar- 
win's original  principle  of  1859,  and  Bateson,  the  most  radical 
thinker  of  the  three,  hold  the  opinion  that  there  is  no  adaptive 
law  observed  in  germ  variation,  but  that  the  chromatin  is  con- 
tinuously experimenting,  and  that  from  these  experiments  se- 
lection guides  the  organism  into  adaptive  and  purposive  Hnes. 
This  is  the  prevailing  opinion  among  most  modern  experimental 
zoologists  and  many  other  biologists. 

Neither  the  Lamarckian  nor  the  Darwinian  explanation 
accords  with  all  that  we  are  learning  through  palaeontology 
and  experimental  zoology  of  the  actual  modes  of  the  origin  and 
development  of  adaptive  characters.  That  there  may  be  ele- 
ments of  truth  in  each  explanation  is  evident  from  the  follow- 
ing consideration  of  our  fundamental  biologic  law.  Adaptive 
characters  present  three  phases:  first,  the  origin  of  character 
form  and  character  function;  second,  the  more  or  less  rapid 
acceleration  or  retardation  of  character  form  and  function;  third, 
the  coordination  and  cooperation  of  character  form  and  func- 
tion. If  we  adopt  the  physicochemical  theory  of  the  origin 
and  development  of  life  it  follows  that  the  causes  of  such 
origin,  velocity  (acceleration  or  retardation)  and  cooperation 
must  lie  somewhere  within  the  actions,  reactions,  and  interac- 
tions of  the  four  physicochemical  complexes,  namely,  the 
physical  environment,  the  developing  organism,  the  heredity- 
chromatin,  the  living  environment,  because  these  are  the  only 
reservoirs  of  matter  and  energy  we  know  of  in  life  history. 

While  it  is  possible  that  the  relations  of  these  four  energy 
complexes  will  never  be  fathomed,  it  is  certain  that  our  search 
for  causes  must  proceed  along  the  line  of  determining  which 
actions,  reactions,  and  interactions  invariably  precede  and 
which  invariably  follow  those  of  the  body  cells  (Lamarckian 
view)   or   those   of   the   chromatin   (Darwin-Weismann  view). 


146 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


The  Lamarckian  view  that  adaptation  in  the  body  cells  invari- 
ably precedes  similar  adaptive  reaction  in  the  chromatin  is  not 
supported  either  by  experiment  or  by  observation;  such  pre- 
cedence, while  occasional  and  even  frequent,  is  by  no  means 
invariable.  The  Darwinian  view,  namely,  that  chromatin 
evolution  is  a  matter  of  chance  and  displays  itself  in  a  variety 
of  directions,  is  contradicted  by  palaeontological  evidence  both 
in  the  Invertebrata  and  Vertebrata,  among  which  we  observe 
that  continuity  and  law  in  chromatin  evolution  prevails  over  the 
evidence  either  of  fortuity  or  of  sudden  leaps  or  mutations,  that 
in  the  genesis  of  many  characters  there  is  a  slow  and  prolonged 
rectigradation  or  direct  evolution  of  the  chromatin  toward  adaptive 
ends.  This  is  what  is  meant  in  our  introduction  (p.  9)  by 
the  statement  that  in  evolution  law  prevails  over  chance. 

Visible  Characters,  Invisible  Chromatin  Determiners 

The  chief  quest  of  evolutionists  to-day  in  every  field  of 
observation  is  the  mode  and  cause  of  the  origin  and  subsequent 
history  of  single  characters.  The  quest  of  Darwin  for  the  causes 
of  the  origin  of  species  has  now  become  an  incidental  or  side 
issue,  since,  given  a  number  of  new  or  modified  heredity  char- 
acters,^ presto,  we  have  a  new  species.  In  this  present  aspect 
of  research  the  discoveries  of  modern  palaeontology  are  in 
accord  with  many  of  the  recently  discovered  laws  of  heredity. 
The  palaeontologist  supports  the  observer  of  heredity  in  dem- 
onstrating that  every  vertebrate  organism  is  a  mosaic  of  an 

*  Character  (Greek,  xapa>tT'^?»  metaph.,  a  distinctive  mark,  characteristic,  character) 
is  the  most  elastic  term  in  modern  biology;  we  may  apply  it  to  everj'  part  and  function 
of  the  organism,  large  or  small,  which  may  evolve  separately  and  be  inherited  separately. 
Mendel  has  shown  that  "characters"  are  far  more  minutely  separable  in  the  invisible 
chromatin  than  they  are  in  the  visible  organism;  also  that  every-  bodily  "character"  is 
a  complex  of  numerous  germ  "characters,"  which  are  technically  known  sls  determiners  or 
factors.  For  example,  such  a  simple  visible  character  as  eye  color  in  the  fruit-fly  is  known 
to  have  determiners  in  the  chromatin.     Morgan,  Thomas  Hunt,  1916,  pp.  118-124. 


CHARACTER   EVOLUTION 


147 


f 


I 


i 


inconceivably  large  number  of  '^characters''  or  "character 
complexes,"  structural  and  functional,  some  indissolubly  and 
invariably  grouped  and  cooperating,  others  singularly  inde- 
pendent. For  example,  the  zoologist  infers  that  every  one  of 
the  most  minute  scales  of  a  reptile  or  hairs  of  a  mammal  is  a 
"character  complex"  having  its  particular  chemical  formulae 
and  chemical  energies  which  condition  the  shape,  the  color, 
the  function,  and  all  other  features  of  the  complex.  Through 
researches  on  heredity  each  of  these  characters  and  character 
complexes  is  now  believed  to  have  a  corresponding  physico- 
chemical  determiner  or  group  of  determiners  in  the  germ- 
chromatin,  the  chromatin  existing  not  as  a  miniature,  but  as 
an  individual  potential  and  causal. 

In  the  course  of  normal  physicochemical  environment,  of 
normal  Hfe  environment,  of  normal  individual  development, 
and  of  normal  selection  and  competition,  an  organism  will  tend 
to  more  or  less  closely  reproduce  its  normal  ancestral  charac- 
ters. But  a  new  or  abnormal  physicochemical  intruder  either 
into  the  environment,  the  developing  individual,  the  heredity- 
chromatin  or  the  Hfe  environment  may  produce  a  new  or  abnor- 
mal visible  character  type.  This  quadruple  nature  of  the 
physicochemical  energies  directed  upon  each  and  every  char- 
acter is  tetrakinetic  in  the  sense  that  it  represents  four  complexes 
of  energy;  it  is  tetraplastic  in  the  sense  that  it  moulds  bodily 
development  from  four  different  complexes  of  causes.  This  law 
largely  underlies  what  we  call  variation  of  t>^e. 

In  other  words,  the  normal  actions,  reactions,  and  inter- 
actions must  prevail  throughout  the  whole  course  of  growth 
from  the  germ  to  the  adult;  otherwise  the  visible  body  (pheno- 
type,  Johannsen)  may  not  correspond  with  the  normal  expres- 
sion of  the  potentialities  of  the  invisible  germ  (genotype,  Jo- 
hannsen). 


I 


148 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


The  principle  of  individuality,  namely,  of  separate  develop- 
ment and  existence,  which  we  have  seen  to  be  the  prime  char- 
acteristic of  the  first  chemical  assemblage  into  an  organism 
(p.  68),  also  governs  each  of  the  character  complexes,  as  ob- 
served by  the  palaeontologist.  In  some  vertebrates  we  observe 
an  infinity  of  similar  character  com- 
plexes, evolving  in  an  exactly  similar 
manner,  as  in  the  beautiful  mark- 
ings of  the  shell  and  the  exquisite 


Fig.  37.  Similarly  Formed  Characters  in  the  Glyptodon. 
Shell  pattern  and  tooth  pattern  of  the  Glyptodon,  a  heavily  armored  fossil  armadillo 
found  in  North  and  South  America.  The  entire  shell  is  covered  with  rosettes,  composed 
of  small  plates  nearly  uniform  in  design,  similar  to  those  in  the  very  small  section  repre- 
sented {A ) .  The  entire  series  of  upper  and  lower  teeth  bear  within  a  uniform  "  glyptic '  ■ 
pattern,  like  that  of  the  tooth  shown  here  (B),  to  which  the  name  Glyptodon  refers. 

enamel  pattern  of  the  teeth  of  the  heavily  armored  armadillo 
known  as  the  glyptodon  (Fig.  37),  in  which  respectively  every 
portion  of  the  shell  evolves  similarly  and  every  one  of  the 
teeth  evolves  similarly,  from  which  we  might  conclude  that 
there  is  an  absence  of  separability  or  individuality  in  form 
characters  and  that  some  homomorphic  (similarly  formative) 
impulse  is  present  in  all  characters  of  similar  chromatin  origin. 
But  such  a  rash  conclusion  is  offset  by  the  existence  of  other 


) 


CHARACTER  EVOLUTION 


149 


character  complexes  of  similar  ancestry  in  which  each  char- 
acter evolves  differently  and  is  in  a  high  degree  heteromorphic 
(diversely  formative),  as,  for  example,  in  the  grinding  teeth  of 

mammals  (Fig.  38). 

This  individuality  and  separability  inherent   in  character 
form  is  equally  observed  in  character  velocity  and  is  the  basis 
of  the  shifting  of  characters  from  adult  to  youthful  stages, 
or  vice  versa,  as  well  as  of  all  the  pro- 
portionate   and   quantitative   changes 
which   make   up   four-fifths   of   verte- 
brate evolution.     Increasing  character 
velocity   is   a   process   of   acceleration; 
decreasing  character  velocity  is  a  proc- 
ess of  retardation.     For  example,  in 
the  evolution   of   any    group    of   ani- 
mals, as  in  plants  (p.  108),  two  char- 
acter   forms    side    by    side,    like    the 
fingers    of    the    hand  or    toes    of   the 
foot,  may  evolve  with  equal  velocity 
and  maintain  a  perfect  symmetry,  or 
one  may  be  accelerated    into   a   very 
rapid   momentum^  while  another  may  be  held  in  a  state  of 
absolute  inertia  or  equilibrium,  and  a  third  may  be  retarded. 
These  are  the  extremes  of  character  velocity  which   result  in 
the  anatomical  or  visible  conditions  respectively  known  as  de- 
velopment, balance,  and  degeneration. 

1  In  physics  momentum  equals  mass  X  velocity.  In  biology  momentum  and  inertia 
refer  to  the  relative  rate  of  character  change,  both  in  individual  development  (ontogeny) 
and  in  evolution  (phylogeny).  Character  parallax  would  express  the  differing  velocities 
of  two  characters.  Thus  the  character  parallax  of  the  right  and  left  horns  in  the  Bron- 
totheriin^  (titanotheres)  is  very  small,  i.  e.,  they  evolve  at  neariy  or  quite  the  same 
rate;  on  the  other  hand,  the  character  parallax  between  the  first  and  second  premolar 
teeth  in  these  animals  is  very  great.  The  character-parallax  idea  has  innumerable  ap- 
plications and  can  be  expressed  quantitatively.     W.  K.  Gregory. 


Fig.  38.  Dissimilarly 
Formed  Characters  of 
Similar  Origin. 

Surface  of  the  upper  grinding 
teeth  of  two  ancient  Eocene 
mammals.  Type  B  is 
known  to  be  related  to 
type  A.  In  Euprotogonia 
{A)  all  the  cusps  are  of  a 
somewhat  similar  rounded 
form.  In  Meniscotherium 
(B)  each  cusp  has  its  own 
peculiar  form. 


ISO 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


The  ever  changing  velocity  and  changing  bodily  form  and 
function  in  character  complexes  are  to  be  regarded  as  expressions 
of  physicochemical  energy  resulting  from  the  actions,  reactions, 
and  interactions  of  different  parts  of  the  organism.  As  we 
have  repeatedly  stated,  these  changes  proceed  according  to 
some  unknown  laws.     The  only  vista  which  we  enjoy  at  pres- 

sent  of  a  possible  fu- 
ture explanation  of  the 
causes  of  character 
origin,  character  veloc- 
ity, and  character  co- 
operation is  through 
chemical  catalysis, 
namely,  through  the 
hypothesis  that  all  ac- 
tions and  reactions  of 
form  and  of  motion 
liberate  specific  cata- 
lytic messengers,  such 
as  ferments,  enzymes, 
hormones,  chalones, 
and  other  as  yet  un- 
discovered chemical  messengers,  which  produce  specific  and 
cooperating  interactions  in  every  character  complex  of  the  organ- 
ism and  corresponding  predispositions  in  the  physicochemical 
energies  of  the  germ;  in  other  words,  that  the  chemical  accelera- 
tors, balancers,  and  retarders  of  body  cell  development  also 
affect  the  germ. 

In  our  survey  of  the  marvellous  visible  evolution  of  the 
vertebrates  we  may  constantly  keep  in  our  imagination  this 
conception  of  the  invisible  actions,  reactions,  and  interactions 
of  the  hard  parts  of  the  structural  tissues,  which  are  preserved 


Fig.  39.     Proportional  Adaptation  in  the 
Fingers  of  a  Lemur. 

This  peculiar  hand  of  the  Aye-Aye  (Chciromys)  of 
Madagascar  affords  an  excellent  example  of  un- 
equal velocity  in  the  development  of  adjacent 
characters.  In  this  hand  each  finger  has  its  own 
proportionate  rate  of  evolution.  The  thumb 
(upper)  is  extremely  short;  the  index  finger  is 
normal;  the  middle  finger  is  excessively  slender, 
in  adaptation  to  a  very  special  purpose,  namely, 
for  insertion  into  small  spaces  and  crevices  in 
search  of  larvae;  the  fourth  and  fifth  fingers  (two 
lower)  are  normal. 


CHARACTER  EVOLUTION 


151 


{ 


f 


Characters 

and 
Character 
Complexes 


in  visible  form  in  fossils.  In  this  field  of  observation  the  nature 
of  the  chemical  and  physiological  influences  of  the  body  can 
only  be  inferred,  while  the  relations  of  these  physicochemical 
influences  to  those  of  the  chromatin  are  absolutely  unknown. 

Such  a  form  of  explanation  would,  however,  only  apply  to  a 
part  of  the  characters  of  adaptation  (table,  page  143).  The 
visible  and  invisible  evolution  of  the  hard  parts  in  adaptation 
resolves  itself  into  six  chief  and  concurrent  processes,  namely: 

Ever  changing  character  form  and  character  function, 

Ever  changing  character  velocity,  acceleration,  balance,  re- 
tardation, in  individual  development  and  in  the  chromatin, 

Ever  changing  character  cooperation,  coordination  and  corre- 
lation, 

Incessant  character  origin  in  the  heredity-chroma  tin,  some- 
times following,  sometimes  antecedent  to  similar  charac- 
ter origin  in  the  developing  individual. 

Relatively  rapid  disappearance  of  character  form  and  charac- 
ter function  in  the  developing  individual, 

Relatively  slow  disappearance  of  the  determiners  and  predis- 
positions of  character  form  and  character  function  in  the 
heredity-chromatin. 

Changes  in  the  visible  bodily  hard  parts  invariably  mirror 
the  invisible  evolution  of  the  chromatin;  in  fact,  this  invisible 
evolution  is  nowhere  revealed  in  a  more  extraordinary  manner 
than  in  the  incessantly  changing  characters  in  such  structures 
as  the  labyrinthine  foldings  of  the  deep  layers  of  enamel  in  the 
grinding  teeth  of  the  horse. 

The  chromatin  as  the  potential  energy  of  form  and  func- 
tion is  at  once  the  most  conservative  and  the  most  progressive 
centre  of  physicochemical  evolution;  it  records  the  body  form 
of  past  adaptations,  it  meets  the  emergencies  of  the  present 
through  the  adaptability  to  new  conditions  which  it  imparts 
to  the  organism  in  its  distribution  throughout  every  living  cell; 
it  is  continuously  giving  rise  to  new  characters  and  functions. 


ti 


9 

152  THE  ORIGIN   AND   EVOLUTION  OF  LIFE 

Taking  the  whole  history  of  vertebrate  life  from  the  beginning, 
we  observe  that  every  prolonged,  old  adaptive  phase  in  a  sim- 
ilar habitat  becomes  impressed  in  the  hereditary  characters  of 
the  chromatin.     Throughout  the  development  of  new  adaptive 
phases  the  chromatin  always  retains  more  or  less  potentiality 
of  repeating  the  embryonic,  immature,  and  more  rarely  some 
of  the  mature  structures  of  older  adaptive  phases  in  the  older 
environments.     This  is  the  basis  of  the  law  of  ancestral  repeti- 
tion, formulated  by  Louis  Agassiz  and  developed  by  Haeckel 
and  Hyatt,  which  dominated  biological  thought  during  thirty 
years  of  the  nineteenth  century  (1865-1895).     It  yielded  with 
more  or  less  success  a  highly  speculative  solution  of  the  ances- 
tral form  history  of  the  vertebrates,  through  the  study  of  em- 
bryonic development  and  comparative  anatomy,  long  before 
the    actual    lines    of    evolutionary    descent    were    determined 
through  palaeontology. 

Laws  of  Form  Evolution  in  Adaptation  to  the  Mechani- 
cal AND  PhYSICOCHEMICAL  ACTIONS,   REACTIONS,   AND 

Interactions    of    Locomotion,    Offense    and 
Defense,  and  Reproduction 

The  form  evolution  of  the  back-boned  animals,  beginning 
with  the  pro-fishes  of  Cambrian  and  pre-Cambrian  time,  ex- 
tends over  a  period  estimated  at  not  less  than  30,000,000 
years.  The  supremely  adaptable  vertebrate  body  t>pe  be- 
gins to  dominate  the  living  world,  overcoming  one  mechan- 
ical difficulty  after  another  as  it  passes  through  the  habitat 
zones  of  water,  land,  and  air.  Adaptations  in  the  motions 
necessary  for  the  capture,  storage,  and  release  of  plant  and 
animal  energy  continue  to  control  the  form  of  the  body  and 
of  its  appendages,  but  simultaneously  the  organism  through  me- 
chanical and  chemical  means  protects  itself  either  offensively 


THE  LAWS  OF  ADAPTATION 


153 


1 


or  defensively  and  also  adapts 
itself  to  reproduce  and  protect 
its  kind,  accordmg  to  Darwin's 
original  conception  of  the  strug- 
gle  for  existence  as   involving 
both  the  life  of  the  individual 
and    the    life    of    its    progeny. 
Among    all    defenseless    forms 
either  speed  or  chemical  or  elec- 
trical   protection    is    a    prime 
necessity,  while  all  heavily  ar- 
mored   forms   gradually   aban- 
don   mobility.     As  among   the 
Invertebrata,   calcium   carbon- 
ate and  phosphate  and  various 
compounds  of  keratin  and  chi- 
tin  are  the  chief  chemical  ma- 
terials of  defensive  armature. 

Locomotion,  as  distinguished 
from  that  in  all  invertebrates, 
is  in  an  elongate  body  stiffened 
by   a   central   axis,   hence   the 
name  chordate  or  Chordata  for 
the    vertebrate    division.     The 
evolution   of   the   cartilaginous 
skeletal  supports  (endoskeleton) 
and   of  the  limbs  is  generally 
from   the   centre   of   the  body 
toward  the  periphery,  the  evolu- 
tion of  the  epidermal  defensive 
armature  (exoskeleton)  is  from 
the  periphery  toward  the  centre. 


MILUONS 

§ 

AGE  OF  MAN            u 

-S                AGE                    w 

^                  OF                     Z 

MAMMALS               ^ 

QUATERNARY 

OF 
YEARS 

§ 

TERTIARY 

■ 

/- 

UPPER 
CRETACEOUS 

S 

3                               0 

■ 

8                              0 

5                    AGE                  N 

LOWER 

5    J 

CRETACEOUS 

2             REPTILES             U) 

(COMANCMEANI 

d     K 

"                                              UJ 
<o                                              — 

s                               ^ 

JURASSIC 

lo- 

oc   0 

t— 

5   .0 

S 

TRIASSIC 

a>-yi  r 

CHIEFLY  UNMETAMORPHOSED:  SEDI 

IGNEOUS  SECONDAR 

NTOMBED  FOSSILS  DIRECT  EVIDENCI 

PERMIAN 

5       PENNSYLVANIAN 

ts- 

AGE 
X>F 

^           AMPHIBIANS 

2                <u»>f>cR 

1         CARBONIFEROO* 

r 

C 

2       MISSISSIPPIAN 

■ 

< 

(LOWER 

U 

CARBONIFEROUS) 

12.  18.000.000  Y 
PALAEOZOIC 

M       DEVONIAN 

20- 

S 

i       SILURIAN 

1£ 

0 

25- 

t- 

X                    AGE 
OF 

1      ORDOVICIAN 

INVERT  kBRATES 

s   

30- 

CAMBRIAN 

KEWEENAWAN 

MILUONS 

OF 

p 

YEARS 

gg 

y 

l|     ANIMIKIAN 

35- 

..     Ui 

EVOLUTION           0 

3 

HURONIAN 

DOMINA 
E.  AND 
ILS  SCA 

INVERTEBRATES      UJ 

1      ALGOMIAN 

* 

t 

40 

■     Ptf 

8 

1      SUDBURIAN 

S^- 

8 

205 

8 

UUK 

!5^£ 

0 

1  q:j^ 

CM 

LAURENTIAN 

45 

LY  METAMORPH 
r  SECONDARY 
T  EVIDENCE  OF 

RATIO 
MEAN) 

i 

50 

CD 

2            EVOLUTION           (J 

^za 

<         UNICEU.ULAR        5 

.2                2 

W    a 

< 

0    * 

E       0. 

I 

55 

-oil                            101       1 

a 

^                  GRENVILLE 

IKEEWATIN) 

ftO 

tCOUTCHlCHINOl 

^^ 

Fig.  40.    Total  Geologic  Time  Scale, 
Estimated  at  Sixty  Million  Years. 

These  estimates  are  based  upon  the 
relative  thickness  of  the  pre-Cambrian 
and  post-Cambrian  rocks.  Prepared 
by  the  author  and  C.  A.  Reeds  after 
the  time  estimates  of  Walcott  and 
Schuchert. 


6  1 


154 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


The  defensive  armature  finally  through  change  of  function 
makes  important  contributions  to  the  inner  skeleton. 

The  chief  advance  which  has  been  made  in  the  last  fifty 
years  is  our  abundant  knowledge  of  the  modes  of  adaptation 
as  contrasted  with  the  very  limited  knowledge  yet  attained 
as  to  the  causes  of  adaptation. 

The  theoretic  application  of  the  fundamental  law  of  action, 
reaction,  and  interaction  becomes  increasingly  difficult  and 
almost  inconceivable  as  adaptations  multiply  and  are  super- 
posed upon  each  other  with  the  evolution  of  the  four  physico- 
chemical  relations,  as  follows: 

Physical  environment:  succession,  reversal,  and  alternation 
of  habitat  zones, 

Individual  development:  succession,  reversal,  and  alterna- 
tion of  adaptive  habitat  phases. 

Chromatin  evolution:  addition  of  the  determiners  of  new 
habitat  adaptations  while  preserving  the  determiners  of 
old  habitat  adaptations. 

Succession  of  life  environments:  caused  by  the  migrations 
of  the  individual  and  of  the  Ufe  environment  itself. 

The  Law  of  Convergence  or  Parallelism  of  Form  in 
Locomotor,  Offensive,  and  Defensive  Adaptations 

There  arise  hundreds  of  adaptive  parallels  between  the 
evolution  of  the  Vertebrata  and  the  antecedent  evolution  of 
the  Invertebrata.  Although  the  structural  body  type  and 
mechanism  of  locomotion  is  profoundly  diverse,  the  combined 
necessity  for  protection  and  locomotion  brings  about  close 
parallels  in  body  form  between  such  primitive  Silurian  euryp- 
terids  as  Biinodes  and  the  vertebrate  armored  fishes  known  as 
ostracoderms,  a  superficial  resemblance  which  has  led  Patten' 
to  defend  the  view  that  the  two  groups  are  genetically  related. 

*  Patten,  Wm.,  191 2. 


Incessant 

Selection 

and 

Competition 


THE  LAWS  OF  ADAPTATION 


-^ss 


ifwut  -A  -mfiii^nt  ?u>k 


5<Rtf»uo»aiit -on  «xt4n<t  Ayllf* 


It  must  be  the  similarity  of  the  internal  physicochemical 
energies  of  protoplasm,  the  similarity  in  the  mechanics  of 
motion,  of  offense  and  defense,  together  with  the  constant  simi- 
larity of  selection,  which  under- 
lies the  law  of  convergence  or 
parallelism  in  adaptation,  name- 
ly, the  production  of  externally 
similar  forms  in  adaptation  to 
similar  external  natural  forces,  a 
law  which  escaped  the  keen  ob- 
servation of  Huxley^  in  his  re- 
markable analysis  of  the  modes 
of  vertebrate  evolution  pub- 
lished in  1880. 

The  whole  process  of  motor 
adaptation  in  the  vertebrates, 
whether  among  fishes,  amphib- 
ians, reptiles,  birds,  or  mam- 
mals, is  the  solution  of  a  series 
of  mechanical  problems,  namely, 
of  adjustment  to  gravity,  of 
overcoming  the  resistance  of 
water  or  air  in  the  develop- 
ment of  speed,  of  the  evolution 
of  the  limbs  in  creating  levers, 
fulcra  (joints),  and  pulleys. 
The  fore  and  hind  fins  of  fishes 
and  the  fore  and  hind  limbs  of  mammals  evolve  uniformly 
where  they  are  homodynamic  and  divergently  where  they  are 
heterodynamic.  This  principle  of  homodynamy  and  hetero- 
dynamy  applies  to  the  body  as  a  whole  and  to  every  one  of  its 


Fig.  41.  Convergent  Adaptation  of 
Form  in  Three  Wholly  Unrelated 
Marine  Vertebrates. 

Analogous  evolution  of  the  swift-swim- 
ming, fusiform  body  type  (upper)  in 
the  shark,  a  fish;  (middle)  in  the 
ichthyosaur,  a  reptile;  and  (lower)  in 
the  dolphin,  a  mammal — three  wholly 
unrelated  animals  in  which  the  in- 
ternal skeletal  structure  is  radically 
different.     After  Osborn  and  Knight. 


» Huxley,  T.  H.,  1880. 


AERIAL 

(flvinq.  volant  typc«) 

Ai:RO-A!=^BORCAL 

^PARACHUTE.   VOLPLANING    TVPt*) 

ARBOREAL 

^CLIMBING.  LCAPING.AND  BBACMIATINO  TVPC«; 


156  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

parts,  according  to  two  laws:  first,  that  each  individual  part 
has  its  own  mechanical  evolution,  and,  second,  that  the  same 
mechanical  problem  is  generally  solved  on  the  same  principle. 

This,  we  observe,  is  invariably 

HABITAT    ADAPTATIONS     O^     THE     VER-  ,  .   ,         ,  '  '      ^  (^r-        ^^r^V^\r^ 

TEBRATEs   TO  THL  CHANGES  OF    thc  idcal  prmcipic,  lor,  unuKC 
^-^^-^-^''*^  n,an,  nature  wastes  little  time 

on  inferior  inventions  but  imme- 
diately proceeds  to  superior  in- 
ventions. 

The  three  mechanical  prob- 

ARBOREO-TERRESTRIAL  r  •     j.  '_.       ♦U^      ,i.rr.f»«. 

(walking  AND  CLIMBING.  8CAN80RIAL  TYPE.)    igms  01  cxistcncc  m  tiie  watcr 

'"''r.lVZ^o..   .Lo...  CUPSO..AL.  .AP.o:    habitat  are:    First,  overcoming 

c'r::;::;;"^"'^  •  °"*^''° •^^^'     the  buoyancy  of  water  either  by 

weighting  down  and  increasing 
the  gravity  of  the  body  or  by 
the  development  of  special  grav- 
itating organs,  which  enable 
animals  to  rise  and  descend  in 

'*'(.lTAc.-Lrv^NTr:';'o «)  this  medium;    second,  the  me- 

FLuviATiLE  chanlcal  problem   of   overcom- 

(frcsh-watcp,     swirr  coprcnt.    slow- 

currcnt;  rLov.o-MAR.Nc  TYPc.j         j^g  ^j^^  resistance  of  water  m 
"*T.VR.ic7!.:.NGANo.uRRo..NG.YPc./  lapld  motiou ,  which  is  accom- 
plished by  means  of  warped  sur- 
faces and  well-designed  entrant 
roVcP?o;?o':-uviNGTYPc,..Low-ANo    and  rc-cutrant    angles    of    the 
—^-"^^  body   similar   to   the   ^^  stream- 

Each  of  the  chief  habitat  zones  may  be  divided  , ,  -         ,  r       .        .  i 

into  many   subzones.     The  vertebrates  may  mi-       hnCS  of      thC      faStCSt      mOdem 

grate   from  one  to  another  of  these  habitats,  or       j^^^^v. 

ZAr'^^r!S^r^"''cL^^o:r:rr::^o-    yachts;    third,  the  problem  of 

tion  result  in  forms  that  are  quadrupedal,  bipedal,  i   •    u    * 

pinnipedal,  apodal,  etc.  prOpulSlOU  01   thC   bOCly,  WnlCll  IS 

accomplished,  first,  by  sinuous  motion  of  the  entire  body,  ter- 
minating in  powerful  propulsion  by  the  tail  fin;  secondly,  by 
supplementary  action  of  the  four  lateral  fins;    third,  by  the 


TERRESTRIO-FOSSORIAL 

(walking   and   burrowing  typcb) 

FOSSORIAL 

(burrowjng  typcb) 

TERRESTRIO-AQUATIC 
(amphibious   types) 

AQUATIC 


MARINE     PELAGIC 

vFREE    SURFACE-LIVING,     DRIFTING,    FLOAT- 
ING.   BCLr-PROPCLLING    TYPCS) 

MARINE      ABYSSAL 


THE  LAWS  OF  ADAPTATION 


157 


horizontal  steering  of  the  body  by  means  of  the  median  sys- 
tem of  fins. 

The  terrestrial  and  aerial  evolution  of  the  four-limbed 
t>pes  (Tetrapoda)  is  designed  chiefly  to  overcome  the  resis- 
tance of  gravity  and  in  a  less  degree  the  resistance  of  the  atmos- 
phere through  which  the  body  moves.  When  the  aerial  stage 
evolves,  with  increasing  speed  the  resistance  of  the  air  becomes 
only  slightly  less  than  that  of  the  water  in  the  fish  stage,  and 
the  warped  surfaces,  the  entrant  and  re-entrant  angles  evolved 
by  the  flying  body  are  similar  to  those  previously  evolved  in 

the  rapidly  moving  fishes. 

In  contrast  with  this  convergence  brought  about  by  the  sim- 
ilarity above  described  of  the  physicochemical  laws  of  action, 
reaction,  and  interaction,  and  the  similarity  of  the  mechanical 
obstacles  encountered  by  the  different  races  of  animals  in 
similar  habitats  and  environmental  media,  is  the  law  of  diver- 
gence. 

Branching  or  Divergence  of  Form,  the  Law  of  Adaptive 

Radiation 

In  general  the  law  of  divergence  of  form,  perceived  by  La- 
marck and  rediscovered  by  Darwin,  has  been  expanded  by 
Osborn  into  the  modern  law  of  adaptive  radiation,  which  ex- 
presses the  differentiation  of  animal  form  radiating  in  every 
direction  in  response  to  the  necessities  of  the  quest  for  nour- 
ishment and  the  development  of  new  forms  of  motion  in  the 
different  habitat  zones.  The  psychic  rudiments  of  this  ten- 
dency to  divergence  are  observed  among  the  single-celled  Pro- 
tozoa (p.  114).  Divergence  is  constantly  giving  rise  to  differ- 
ences in  structure,  while  convergence  is  constantly  giving  rise 
to  resemblances  of  structure. 

The  law  of  adaptive  radiation  is  a  law  expressing  the  modes 


iS8 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


THE  LAWS  OF  ADAPTATION 


159 


Law 
of 

Adaptive 
Radiation 

in  the 

External 

Body 

Form 


of  adaptation  of  form,  which  fall  under  the  following  great 
principles  of  convergence  and  divergence: 

1.  Divergent  adaptation,  by  which  the  members  of  a  primitive 
stock  tend  to  develop  differences  of  form  while  radiating 
into  a  number  of  habitat  zones. 

2.  Convergent  adaptation,  parallel  or  homoplastic,  whereby  an- 
imals from  different  habitat  zones  enter  a  similar  habitat 
zone  and  acquire  many  superficial  similarities  of  form. 

3.  Direct  adaptation,  for  example,  in  primar\'  migration  through 
an  ascending  series  of  habitat  zones,  aquatic  to  terres- 
trial, arboreal,  aerial. 

4.  Reversed  adaptation,  where  secondary  migration  takes  a  re- 
verse or  descending  direction  from  aerial  to  arboreal, 
from  arboreal  to  terrestrial,  from  terrestrial  to  aquatic 
habitat  zones. 

5.  Alternate  adaptation,  where  the  animal  departs  from  an  orig- 
inal habitat  and  primary  phase  of  adaptation  into  a  sec- 
ondary phase,  and  then  returns  from  the  secondary  phase 
of  adaptation  into  a  more  or  less  perfect  repetition  of  the 
primary  phase  by  returning  to  the  primary  habitat  zone. 

6.  Change  of  adaptation  (function),  by  which  an  organ  serving  a 
certain  function  in  one  zone  is  not  lost  but  takes  up  an 
entirely  new  function  in  a  new  zone. 

7.  Symbiotic  adaptation,  where  vertebrate  forms  exhibit  recip- 
rocal  or  interlocking  adaptations  with  the  form  evolution 
of  other  vertebrates  or  invertebrates. 

It  is  very  important  to  keep  in  mind  that  the  body  and 
limb  form  developed  in  each  adaptive  phase  is  the  starting 
point  of  the  next  succeeding  phase. 

Prolonged  residence  by  an  animal  type  in  a  single  habitat 
zone  results  in  profound  alterations  in  its  chromatin  and  in 
consequence  the  history  of  past  phases  is  more  or  less  clearly 

recorded. 

Among  the  disadvantages  of  prolonged  existence  in  one  life 
zone  are  the  following:  Through  the  law  of  compensation,  dis- 
covered by  Geoffroy  St.  Hilaire  early  in  the  last  century,  every 
vertebrate,  in  developing  and  specializing  certain  organs  sacri- 


I 


fices  others;  for  example,  the  lateral  digits  of  the  foot  of  the 
horse  are  sacrificed  for  the  evolution  of  the  central  digit  as  the 
animal  evolves  from  tridactylism  to  monodactyUsm.     These 
sacrificed  parts  are  never  regained;  the  horse  can  never  regain 
the    tridactyl   condition   although   it  may  re-enter  a  habitat 
zone  in  which  three  digits  on  each  foot  would  serve  the  pur- 
poses of  locomotion  better  than  one.     In  this  sense  chromatin 
evolution  is  irreversible.     The  extinction  of  vertebrate  races 
has  generally  been  due  to  the  fact  that  the  various  types  have 
sacrificed  too  many  characters  in  their  structural  and  func- 
tional reactions  to  a  particular  life  habitat  zone.     A  finely  spe- 
cialized form  representing  a  perfect  mechanism  in  itself  which 
closely   interlocks  with   its  physical   and  living  environment 
reaches  a  cul-de-sac  of  structure  from  which  there  is  no  possible 
emergence  by  adaptation  to  a  different  physical  environment 
or  habitat  zone.     It  is  these  two  principles  of  too  close  adjust- 
ment to  a  single  environment  and  of  the  non-revival  of  char- 
acters once  lost  by  the  chromatin  which  underly  the  law  that 
the  highly  specialized  and  most  perfectly  adapted  types  become 
extinct,  while  primitive,   conservative,   and  relatively  unspe- 
cialized  types  invariably  become  the  centres  of  new  adaptive 
radiations. 


i 


CHAPTER  VI 

EVOLUTION  OF  BODY  FORM  IN  THE    FISHES  AND 

AMPHIBIANS 

Rapid  evolution  in  a  relatively  constant  environment.  Mechanism  of  motion, 
of  offense,  and  defense.  Early  armored  fishes.  Primordial  sharks.  Rise 
of  existing  groups  of  fishes.  Form  evolution  of  the  amphibians.  Maxi- 
mum radiation  and  extinction. 

A  SIGNIFICANT  kw  of  fish  evolution  is  that  in  a  practically 
unchanging  environment,  that  of  salt  and  fresh  water,  which  is 
relatively  constant  both  as  to  temperature  and  chemical  con- 
stitution as  compared  with  the  variations  of  the  terrestrial 
environment,  it  is  steadily  progressive  and  reaches  the  great- 
est extremes  of  form  and  of  function.  This  indicates  that  a 
changing  physicochemical  environment,  although  important,  is 
not  an  essential  cause  of  the  evolution  of  form.  The  same 
law  holds  true  in  the  case  of  the  marine  invertebrates  (p.  137), 
as  observed  by  Perrin  Smith.  A  second  principle  of  signifi- 
cance is  that  even  the  lowliest  fishes  establish  the  chief  glandu- 
lar and  other  organs  of  action,  reaction,  and  interaction  which 
we  observe  in  the  higher  types  of  the  vertebrates.  Especially 
the  glands  of  internal  secretion  (p.  74),  the  centres  of  inter- 
action and  coordination,  are  fully  developed. 

Mechanism  of  Motion,  of  Offense,  and  Defense 

Ordovician  time,  the  early  Palaeozoic  Epoch  next  above  the 
Cambrian,  is  the  period  of  the  first  vertebrates  known,  namely, 
the  fossil  remains  of  fish  dermal  defenses  found  near  Canon 
City,  Col.,  as  announced  by  Walcott  in  1891,  and  subse- 
quently   discovered    in    the    region    of    the    present    Bighorn 

160 


EARLIEST  KNOWN  FISHES 


161 


Mountains  of  Wyoming  and  the  Black  Hills  of  South  Dakota. 
Small  spines  referred  to  acanthodian  sharks  are  also  abundant 
in  the  Ordovician  of  Canon  City,  Col.  Since  they  were  slow- 
moving  types  protected  with  the  beginnings  of  a  dorsal  arma- 
ture  composed   of  small   calcareous   tubercles,   to   which   the 


FISHES 


AMPHIBIANS     REPTILES 


BIROS 


MAMMALS 


ORDER  OF  APPEARANCE  AND  EXPANSION  OF  THE  CLASSES  OF  VERTEBRATE  ANIMALS 


Fig.  42.    Chronologic  Chart  of  Vertebrate  Succession. 
Successive  geologic  appearance  and  epochs  of  maximum  adaptive  radiation  (expansion) 
and  diminution  (contraction)  of  the  five  classes  of  vertebrates,  namely,  fishes,  amphi- 
bians, reptiles,  birds,  and  mammals. 

group  name  Ostracoderm  refers,  probably  these  earHest  known 
pro-fishes  were  not  primitive  in  external  form  but  followed 
upon  a  long  antecedent  stage  of  vertebrate  evolution.  In  the 
form  evolution  of  the  vertebrates  relatively  swift-moving,  de- 
fenseless types  are  invariably  antecedent  and  ancestral  to  slow- 
moving,  armored  types.  Ancestral  to  these  Ordovician  chor- 
dates  there  doubtless  existed  free-swimming,  quickly  darting 


l62 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


types  of  unarmored  fishes.  The  double-pointed,  fusiform  body, 
in  which  the  segmented  propelling  muscles  are  external  and  a 
stiffening  notochord  is  central,  is  the  fish  prototype,  which 


HYOMCReS 
[Hutcle  itgmtntt) 


DIGESTIVE  THACT 


WU  SUTS 


more  or  less  clearly 
survives  in  the  exist- 
ing lancelets  {Amphi- 
oxiis)  and  in  the  lar- 
val stages  of  the  de- 
generate ascidians. 
These  animals  also 
furnish  numerous 
embryonic  and  lar- 
val proofs  of  de- 
scent from  nobler 
types. 

Following  the 
pro-fishes  of  Ordovi- 
cian  time,  the  great  group  of  true  fishes  begins  its  form  evolu- 
tion with  {A)  active,  free-swimming,  double-pointed  types  of 
fusiform  shape,  adapted  to  rapid  motion  through  the  water 
and   to   predaceous   habits   in   pursuit   of   swift-moving   prey. 


Fig.  43.    The  Existing  Lancelets  {Ampkioxus). 

Fusiform  protochordates  living  in  the  littoral  zone  of 
the  ocean  shores,  sole  survivors  of  an  extremely 
ancient  stage  of  chordate  (pro-vertebrate)  evolution. 
The  body  is  fusiform  or  doubly  pointed,  hence  the 
name  Amphioxits.  It  is  stiffened  by  the  continuous 
central  axis  (chorda,  notochord).  All  the  other  or- 
gans are  more  or  less  sharply  segmented.   After  Willey. 


'^ 


EARLIEST  KNOWN   FISHES 


163 


From  this  type  there  radiated  many  others:  (B)  the  deep, 
narrow-bodied  fishes  of  relatively  slow  movements,  frequenting 
the  middle  depths  of  the  waters;  {D)  the  swift-moving,  elongate 


B 


COMPRESSED  (DEEP-BODIEOI 


A 


FUSIFORM-COMPRESSED 


APODAL  (ELONGATE.  EEL-LIKE) 


c 


DEPRESSED  <GROVELINGI 


Fig.  44.  The  Five  Principal  Types  of  Body  Form  in  Fishes. 
These  begin  with  (A)  the  swift-moving,  compressed,  fusiform  types  which  pass,  on  the 
one  hand,  into  (B)  laterally  compressed,  slow-moving,  deep-bodied  types,  and,  on  the 
other,  into  (C)  laterally  depressed,  round,  bottom-dwelling,  slow-movmg  types,  also 
into  (D)  elongate,  swift-moving  fusiform  types  which  grade  into  (£)  the  eel-like,  swift- 
moving,  bottom-living  types  without  lateral  fins.  These  five  types  of  body  form  m 
fishes  arise  independently  over  and  over  again  in  the  various  groups  of  this  class  ot 
vertebrates  Partially  convergent  forms  subsequently  appear  among  amphibians,  rep- 
tiles and  mammals.  Prepared  for  the  author  by  W.  K.  Gregory  and  Erwin  S.  Chnstman. 


1 1 


n  ■ 


UPPER' 
SILURIAf*  .\ 


164  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

types  which  increasingly  depend  upon  lateral  motions  of  the 
body  for  propulsion  and  thus  tend  to  lose  the  lateral  fins  and 

finally  to  assume  (£)  an 
elongate,  eel  shape,  en- 
tirely   finless,    for    pro- 
gression along  the  bot- 
tom;    (C)    the  bottom- 
living   forms,   in   which 
the  body  becomes  later- 
ally broadened,  the  head 
very  large  relatively  and 
covered  with  protective 
dermal    armature,    the 
movements  of  the  ani- 
mals   becoming    slower 
and  slower  as  the  dermal 
defenses  develop.     This 
law   applies   to   all   the 
vertebrates,  including 
man,   namely:    the  de- 
velopment of  armor  is 
pari  passu  with  the  loss 
of   speed.      Conversely, 
the  gain  of  speed  neces- 
sitates   the    loss    of  ar- 
mor.       Smith      Wood- 
ward^ has  traced  similar 
radiations  of  body  form  in  the  historic  evolution  of  each  of  the 

great  groups  of  fishes. 

The  interest  of  this  fivefold  law  of  body-form  radiation  is 
greatly  enhanced  when  we  find  it  repeated  successively  under 

1  Smith  Woodward,  A.,  1915. 


PALEOGEOGRAPHY.  UPPER  SILURIAN  (SALINA)  TIME 
AFTER  SCMUCHEHT,  APRIL  !»'• 
^  MARINE  DEPB6ITS         f   CONTINENTAL  DEPOSITS        .    SALT  DEPOSITS 


■  ■VOLCANOEC 


Fig.  45.    North  America  in  Upper  Silurian 

Time. 

During  this  period  of  depression  of  the  Appala- 
chian region  and  elevation  of  the  western  half  of 
the  North  American  continent  occurred  the 
maximum  evolution  of  the  most  primitive  armored 
fishes,  known  as  Ostracoderms,  which  were 
widely  distributed  in  Europe,  America,  and  the 
Antarctic.     After  Schuchert,  1916. 


EARLY  ARMORED   FISHES 


165 


^ 


the  law  of  convergence  among  the  aquatic  amphibia,  reptiles, 
and  mammals  as  one  of  the  invariable  effects  of  the  coordina- 
tion of  the  mechanism  of  locomotion  with  that  of  offense  and 
defense.  In  each  of  these  four  or  five  great  radiations  of  body 
form,  from  the  swift-moving 


to  the  bottom-  or  ground- 
living,  slow,  armored  types, 
there  is  usually  an  increase  of 
bodily  size,  also  an  increase  of 


^j  Pill  I  ui  Huaiw  I 


:? 


Fig.   46.    The   Ostracoderm  Palceaspis 
OF  Claypole  as  Restored  by  Dean. 


specialization,  the  maximum  in  both  being  reached  just  before 
the  period  of  extinction  arrives. 

Early  Armored  Fishes 
The    armored    Ordovician    ostracoderms    are    very    Httle 
known.     The   Upper   Silurian    ostracoderms    enjoyed   a   wide 

distribution  in  Europe  and 
America.  They  include 
both  the  fusiform,  free-swim- 
ming type  {Birkenia)  and 
the  broadly  depressed  ray- 
like types  {Lanarkia,  etc.). 
Apparently  they  had  not 
yet  acquired  cartilaginous 
lower  jaws  and  were  in  a 
lower  stage  of  evolution  than 
the  true  fishes. 

The  armature  is  from 
the  first  arranged  in  shield 
and  plate  form,  as  seen  in 
Palceaspis,  from  the  Upper 
Silurian  Salina  time  of  Schu- 
chert.    In    this    epoch    we 


Fig.  47.    The  Antiarchi. 

Armored,  bottom-living  Ostracoderm  type,  Bo- 
//ir/(7/c/>/5^,  from  the  Upper  Devonian  of  Canada, 

with  chitinous  armature  and  a  pair  of  anterior 
appendages  analogous  to  those  of  the  euryp- 
terid  crustaceans.  This  cluster  of  animals  was 
undoubtedly  buried  simultaneously  while 
headed  against  the  current  in  search  of  food 
or  for  purposes  of  respiration.     After  Patten. 


1 66  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

obtain  our  first  glimpses  of  North  American  land  life  in  the 
presence  of  the  oldest  known  air-breathing  animals,  the  scorpion 

spiders,  also  of  the  first  known 
land  plants.  There  are  indica- 
tions of  an  arid  climate  in  many 
parts  of  the  world. 

In  Upper  Silurian  time  the 
ostracoderms   attain    the   slow, 
armored,  bottom-living  stage  of 
evolution,  typified  in  the  ptera- 
spidians    and    cephalaspidians, 
which  were  widely  distributed 
in  Europe,  in  America,  and  pos- 
sibly in  the  Antarctic  regions, 
as  indicated  by  recent  explora- 
tions there.     Belonging  to  an- 
other and  very  distinct  order,  or 
subclass  ( Antiarchi) ,  are  certain 
armored  Devonian  forms  {Both- 
riolepiSj  Pterichthys,  etc.),  which 
possessed  a  pair  of  jointed  lat- 
eral   appendages.     Some    of 
these  fishes,  which  are  propelled 
by   a   pair   of   appendages   at- 
tached to  the  anterior  portion 
of  the  body,  present  analogies  to 
the  eur>T)terids  (Merostomata, 
or  Arachnida). 

In  the  fresh-water  deposits 
of  Lower  Devonian  age  have 
been  discovered  the  ancestors  of 
the     heavily     armored     fishes 


PRIMORDIAL   SHARKS 


167 


Fig.  48.    The  Arthrodira. 

(Above.)  Restoration  of  the  gigantic 
Middle  Devonian  Arthrodiran  (jointed 
neck)  fish  Dinichthys  intermedins,  eight 
feet  in  length,  of  the  Cleveland  shales 
(Ohio),  showing  the  bony  teeth  and 
bony  armature  of  the  head  region. 
(Below.)  Lateral  view  of  the  same. 
Model  by  Dr.  Louis  Hussakof  and  Mr. 
Horter,  in  the  American  Museum  of 
Natural  History. 


4 


i 


known  as  the  Arthrodira,  a  group  of  uncertain  relationships. 
They  have  many  adaptations  in  common  with  Bothriolepis, 
such  as  the  jointed  neck,  dermal  jaws,  carapace,  plastron,  and 
paired    appendages    {AcantJiaspis),     Some    authorities    regard 
the  Arthrodira  as  aberrant  lung-fishes.     Dean,  Hussakof,  and 
others  regard  the  balance  of  evidence  as  in  favor  of  relationship 
with  the  stem  of  the  Antiarchi  {Bothriolcpis),     In  the  Middle 
Devonian  (the  Cleveland  shales 
of  Ohio)  they  attain  the  formi- 
dable size  shown  in  the  species 
Dinichthys  intcrmcdius  (Fig.  48). 
Like   the   ostracoderms,    these 
animals  are  not  in  the  central 
or  main  lines  of  fish  evolution 
but    represent    collateral    lines 
which  early  attained  a  very  high 
degree  of   specialization  which 
was  followed  by  extinction. 

Primordial  Sharks,  Ances- 
tral TO  Higher  Ver- 
tebrates 


Fig.  49.    A  Primitive  Devonian  Shark. 

(Above.)  Cladosclachc,  the  type  of  the 
primitive  Devonian  shark  of  Ohio  with 
paired  and  median  lappet  fins  provided 
with  rod-like  cartilaginous  supports, 
from  which  type  by  fusion  the  limbs  of 
all  the  higher  land  vertebrates  have 
been  derived.  Model  by  Dean,  Hussa- 
kof, and  Horter  from  specimens  in  the 
American  Museum  of  Natural  History. 
(Below.)  The  interior  structure  of 
the  lappet  fins  of  Cladosclachc  showing 
the  cartilaginous  rays  (white)  within 
the  fin  (black).     After  Dean. 


The  central  line  of  fish 
evolution,  destined  to  give  rise 
to  all  the  higher  and  modern 
fish  t>T>es,  is  found  in  the  typical  cartilaginous  skeleton  and  jaws 
and  four  fins  of  the  primordial  sharks,  the  primitive  fusiform 
stage  of  which  appears  in  the  spine-finned  t>^e  (acanthodian, 
Diplacanthus,  Fig.  51)  of  Upper  Silurian  time.  The  relatively 
large-headed,  bottom-living  t>T)es  of  sharks  do  not  appear  until 
the  Devonian,  during  which  epoch  the  early  swift-moving, 
fusiform,  predaceous  types  through  a  partly  reversed  adaptation 


i 


1 68  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

branch  off  into  the  elongated  eel-shaped  forms  of  the  Car- 
boniferous. 

The  prototype  of  the  shark  group  is  the  Cladosclache  (Fig. 
49),  a  fish  famed  in  the  annals  of  comparative  anatomy  since 
it  demonstrates  that  the  fins  of  fishes  arise  from  lateral  skin 


■JLand-verte-I 


PENNSYLVANIAN 

CAKaoNmaouv 


M1ES1SS1PPIAN 

•LOWER 
CAfWONirEHOlW 


OROOVICIAN 


7  SOFT  SKINNED  CHORDATES 


ORIGIN  AND  ADAPTIVE  RADIATION  OF  THE  FISHES 


W  K  OnCOOKY.  t*l« 


Fig.  50.  Origin  and  .\daptive  R.u)iation  of  the  Fishes. 
This  chart  shows  the  now  extinct  Siluro- Devonian  groups,  the  Ostracodcrms  and  Arthro- 
dires,  in  relation  to  the  surviving  lampreys  (Cyclostomes) ;  sharks  and  rays  (Llasmo- 
branchs);  sturgeons,  garpikes,  and  bowfins  (Ganoids);  bony  fishes  (Teleosts);  primi- 
tive and  recent  lung-fishes  (Dipnoi);  and  finally  the  fringe-finned  or  lobe-finned  Ganoids 
(Crossopterygii)  from  the  cartilaginous  fins  of  which  the  fore  and  hmd  limbs  of  the 
first  land-living  vertebrates  (Tetrapoda)  were  derived.  Dotted  areas  represent  groups 
which  still  exist.  Hatched  areas  represent  extinct  groups.  Prepared  for  the  author 
by  W.  K.  Gregory. 

folds  of  the  body,  into  which  are  extended  internal  stiffening 
cartilaginous  rods  (Fig.  49)-  ^^  ^^^urse  of  evolution  these 
rods  are  concentrated  to  form  the  central  axis  of  a  freely  jointed 
fin,  while  in  a  further  step  of  evolution  they  transform  into  the 
cartilages  and  bones  of  the  limb  girdles  and  limb  segments  of 
the  four-footed  land  vertebrates,  the  Tetrapoda. 

The  manner  of  this  fin  and  Umb  transformation  has  been 
one  of  the  greatest  problems  in  the  history  of  the  origin  of 


\ 


\ 


RISE  OF  MODERN  FISHES 


169 


animal  form  since  the  earliest  researches  of  Carl  Gegenbaur, 
of  Heidelberg,  who  sought  to  derive  the  lateral  fins  from  a 
modification  through  a  profound  change  of  adaptation  (func- 
tion) of  the  cartilaginous  rods  which  support  the  respiratory 
gill  arches.     While  palaeontology   has  disproved  Gegenbaur's 
hypothesis  that  the  limbs  of  the  higher  vertebrates,  including 
those  of  man,  are  derived  from  the  cartilaginous  gill  arches  of 
fishes    it  has  helped  to  demonstrate  the  truth  of  Reichert's 
anatomical  hypothesis  that  the  bony  chain  of  the  middle  ear 
of  man  has  been  derived  through  change  of  adaptation  from  a 
portion  of  a  modified  gill  arch,  namely,  the  mandibular  carti- 
lage of  the  fish. 

The  cycle  of  shark  evolution  in  course  of  geologic  time 
embraces  a  majority  of  the  swift-moving,  predaceous  types, 
which  radiate  into  the  sinuous,  elongate  body  of  the  frilled 
shark  (Chlamydoselache)  and  into  forms  with  broadly  depressed 
bodies,  such  as  the  bottom-living  skates  and  rays.  Under  the 
law  of  adaptive  radiation  the  sharks  seek  every  possible  habitat 
zone  except  the  abyssal  in  the  search  for  food.  The  nearest 
approach  to  the  evolution  of  the  eel-shaped  type  among  the 
sharks  are  certain  forms  discovered  in  Carboniferous  time. 

Rise  of  Modern  Fishes 

By  Upper  Devonian  time  the  fishes  in  general  had  already 
radiated  into  all  the  great  existing  groups.  The  primitive 
armored  arthrodires  and  ostracoderms  were  nearing  extinc- 
tion The  sharks  were  still  in  the  early  lappet-fin  stage  of 
evolution  above  described,  a  common  characteristic  of  the 
members  of  this  entire  order  being  that  they  never  evolved  a 
solid  bony  armature,  finding  sufficient  protection  in  the  sha- 
green covering. 

The  scaled  armature  of  the  first  true  ganoid,  enamel-cov- 


1 


lyo  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

ered  fishes  {Osteolcpis,  Chcirolepis)  now  makes  its  first  appear- 
ance. These  armored  knights  of  the  sea  are  descended  from 
simpler  scaly  forms  which  also  gave  rise  to  the  rich  stock  of 
sturgeons,  garpikes,  bowfins,  and  true  bony  fishes  (teleosts) 
which  now  dominate  all  other  fish  groups  both  in  the  fresh 


Fig.  51.    Fish  Types  from  the  Old  Red  Sandstone  of  Scotland. 

Upper  Devonian  time.  Primitive  ganoids,  primitive  spine-fmned  sharks,  bottom-living 
Ostracoderms,  partly  armored  ganoids,  and  the  first  lung-fishes,  i.  Osteolepis,  primitive 
lobe-finned  ganoid.  2.  Holopiychius,  fringe-finned  ganoid.  3,  6.  Chciracauthus,  spine- 
finned  shark  (Acanthodian).  4.  Diplacanthus,  spine-finned  shark  (.\canthodian). 
5.  Cofr(?5/g«5,  primitive  Arthrodiran.  7.  C/?r/ro/<'/>/5,  primitive  ganoid.  8,  q.  Diplerus, 
primitive  lung-fish.  Pterichthys,  bottom-living  Ostracoderm  allied  to  Bothriolcpis. 
Restorations  by  Dean,  Hussakof,  and  Horter,  partly  after  Traquair.  Models  in  the 
American  Museum  of  Natural  History. 

waters  and  the  seas.  Remotely  allied  to  this  stock  are  the 
first  air-breathing  lung-fishes  (Dipnoi),  represented  by  Dipterus; 
also  the  ^^lobe-finned,"  or  ^^fringe-finned"  ganoids  from  which 
the  first  land  vertebrates  wxre  derived.  From  a  single  locality, 
in  the  Old  Red  Sandstone  of  Scotland,  Traquair  has  recovered 


RISE  OF   MODERN  FISHES 


171 


a  w^hole  fossil  series  of  these  archaic  fish  types  as  they  lived 
together  in  the  fresh  water  or  the  brackish  pools  of  Upper  De- 
vonian time.     (Fig.  51). 

In  this  period  the  palaeogeographers  (Schuchert)  obtain  their 
first  knowledge  of  the  evolution  of  the  terrestrial  environment 
in  the  indications  of  the  existence  of  parallel  mountain  ranges 
on  the  British  Isles,  of  active  volcanoes  in  the  Gaspe  region  of 


PAUEOCEOGRAFHY.  EARLY  LOWER  DEVONIAN  (HELDERBERGIAN.GE01NN.AN.HERCYN.AN-K0N.EPRUSSIAN)  TIME 

*nEB  SCHUCMEKT,  APRIU  1916 
>«^MARIWE  OCPOSITS        ,?^COWTmENT»L  DEPOSITS       ,.■  MOUNTAINS  *HD  VOLCANOeS 


Fig.  52.    Theoretic  World  Environment  in  Early  Lower  Devonian  Times. 
The  period  of  the  early  appearance  of  terrestrial  invertebrates  and  vertebrates.     This 
shows  the  hvmthetical  South  Atlantic  continent  Gondu^ana  and  the  Kurasiatic  inland 
sea  Tdhys,  according  to  the  hypotheses  of  Suess.     Modified  after  Schuchert,  1916. 

New  Brunswdck,  of  the  mountain  formations  of  South  Africa, 
and  of  the  depressions  of  the  centre  of  the  Eurasiatic  continent 
into  the  great  central  Mediterranean  Sea,  known  as  the  Tcthys 
of  the  great  Austrian  geologist,  Suess.  In  the  seas  of  this  time, 
as  compared  with  Cambrian  seas,  we  observe  that  the  trilo- 
bites  are  in  a  degenerate  phase,  the  brachiopods  are  relatively 
less  numerous,  the  echinoderms  are  represented  by  the  bottom- 


172  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

living  starfishes,  sharks  are  abundant,  and  arthrodiran  fishes  are 
still  abundant  in  Germany. 

It  was  long  believed  that  the  air-and-water-breathing  Am- 
phibia evolved  from  the  Dipnoi,  the  air-breathing  fishes  of  the 
inland  fresh  waters,  and  this  hypothesis  was   stoutly  main- 


1 


i 


/ 


mif> 


FIN  STAGE 

RHIPIDISTIAN  FISH 
(OEVONIANt 


FOOT  STAGE 

AMPHIBIAN 
•CARBONIFEROUS) 


n 


-  ^    _ 

':I5^ 

-  •  1  *- 

(   0 

•■•/' 

^ —  J 

Fig.  S3-    Change  of  Adaptation  in  the  Limbs  of  Vertebrates. 
The  upper  figures  represent  the  theoretic  mode  of  metamorphosis  of  the  fringe-fin  of  the 
Crossopterygian  fish   (left)  into  the  foot  of  an  amphibian  (right)  through    oss  of  the 
dermal  fringe  border  and  rearrangement  of  the  cartilaginous  supports  of  the  lobe. 

After  Klaatsch.  ,      ,   ,.  •  •     i        i  *•         t  tu^ 

The  lower  figures  represent  (left)  the  theoretic  mode  of  direct  origmal  evolution  of  the 
bones  of  the  fringe-fin  {A,B)  of  a  Crossopterygian  fish-the  Rhipidislia  type  of  Cope- 
into  the  bony,  five-rayed  limb  (C)  of  an  amphibian  of  the  Carboniferous  Epoch  (after 
Gregory)-  and  (right)  the  secondarv,  reversed  evolution  of  the  five-rayed  limb  of  a 
land  reptile  {A)  into  the  fin  or  paddle  (5,  C)  of  an  ichthyosaur  (after  Osborn). 

tained  by  Carl  Gegenbaur,  who  also  upheld  what  he  termed 
the  archipterygian  theory  of  the  origin  of  the  vertebrate  limb, 
namely,  that  the  protot>^e  of  the  modern  limbed  forms  of 
terrestrial  vertebrates  is  to  be  found  in  the  fin  of  the  modern 
Australian  lung-fish,  Ceratodus.  This  hypothesis  of  Gegen- 
baur,  which  has  been  warmly  supported  by  a  talented  group  of 
his  students,  is  memorable  as  the  last  of  the  great  hypotheses 
regarding  vertebrate  descent  to  be  founded  exclusively  upon 


RISE  OF   MODERN   FISHES 


173 


Fig.  54.    Extremes  of  Adaptation  in 
Locomotion  and  Illumination. 
Extremes  of  adaptation  in  the  existing  bony 
fishes  (Teleosts)  of  the  Abyssal  Zone  of 
the  Oceans.     Although  many  different  or- 
ders of  Teleosts  arc  represented,  each  type 
has  independently  acquired   phosphores- 
cent organs,  affording  a  fine  example  of 
the   law  of  adaptive  convergence.     The 
body  form   in   these    fishes    is    of    great 
diversity,      i.  Thread-eel,   Nemichthys 
scolopaceus  Richardson.      2.  Barathromis 

diabhanusBrauer.  x.  Neoscopehts  macrolc-  .         ,     ^r     • 

S:  Johnson.  4  5.  Ga/ros,o,„us  bairdi  Gill  and  Ryder.  6.  0•mn>acUsra,,ko^^n^ 
Brauor  7  Slcrnopiyx  diaplm.a  Lowe.  8.  GiganUna  chum  Brauer  9.  Mdanoslomras 
rlZnlips  Brauer.  .0.  SiylopM^^Uuns  paradoxus  Brauer.  ...OpMoproctus  solcaU.s 
Vaillant.     .\fter  models  in  the  iVmerican  Museum  of  Natural  History. 

comparative  anatomy  and  embryology  as  opposed  to  the 
triple  evidence  afforded  by  these  sciences  when  reinforced  by 
paleontology. 


174 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


RISE  OF  MODERN  FISHES 


175 


It  is  through  the  discovery  of  primitive  types  of  the  fringe- 
fmned  ganoids,  to  which  Huxley  gave  the  appropriate  name 
Crossopterygia,  in  reference  to  the  fringe  of  dermal  rays  around 
a  central  lobe-fin  of  cartilaginous  rods,  that  the  true  ancestry 
of  the  Amphibia  and  of  the  amphibian  limb  has  been  traced. 
This  is  now  regarded  as  due  to  a  partial  change  of  adaptation, 


riG.    55.      I'HOSFIIORKSCLNT    ILLUMINATING   URGANS. 

The  abyssal  fishes  represented  in  Fig.  54  as  they  are  supposed  to  appear  in  the  darkness 
of  the  ocean  depths.     After  models  in  the  American  Museum  of  Natural  History. 

incident  to  the  passage  of  the  animal  from  the  littoral  life  zone 
to  the  shore  zone,  whereby  the  propelling  fin  was  gradually 
transformed  into  the  propeUing  limb.  This  transformation 
implies  a  long  terrestrio-aquatic  phase,  in  which  the  fin  was 
partly  used  for  propulsion  on  muddy  surfaces  (Fig.  53). 

In  the  reversed  parallel  retrogressive  evolution  of  the  lung- 
fishes  {Lepidosiren^  Gymnotiis)^  of  the  fringe-finned  fishes  (Cala- 
nioichthys)  and  of  the  bony  fishes  {AngiiiUa),  the  final  eel-shaped, 


finless  stage  is  through  convergent  adaptation  either  approached 
or  actually  passed. 

The  bony  fishes  (teleosts),  which  first  emerge  as  a  distinct 
group  in  Jurassic  time,  radiate  adaptively  into  all  the  great 
body-form  types  which 
had  been  previously  at- 
tained by  the  older 
groups,  more  or  less 
closely  imitating  each 
in  turn,  so  that  it  is  not 
easy  to  distinguish  su- 
perficially between  the 
armored  catfishes  {Lori- 
carid)  of  the  existing 
South  American  waters 
and  their  prototypes 
(Cephalaspis)  of  the 
early  Palaeozoic.  The 
most  extreme  specializa- 
tion in  the  great  group 
of  bony  fishes  is  to  be 
found  in  the  radiations 
of  abyssal  fishes  into 
slow-  and  swift-moving 
forms  which  inhabit  the 
great  depths  of  the 
ocean  and  are  adapted 
to  tons  of  water-pres- 
sure, to  temperatures 
just  above  the  freezing 
point,  and  to  total  absence  of  sunlight  which  is  compensated 
for  by  the  evolution  of  a  great  variety  of  phosphorescent  light- 


PALEOGEOGRAPHY,  UPPER  DEVONIAN  (GENESEE-PORTAGE)  TIME 
AFTER  SCHUCHERT,  APRIL,  181* 

^^ MARINE  DEPOSITS       ^'  CONTINENTAL  DEPOSITS         ...MOUNTAINS  AND  VOLCANOES 

.  .  DEEP  WELLS 


Fig.  56.    North  America  in  Upper  Devonian  Time. 

The  maximum  evolution  of  the  Arthrodiran  fishes 
{DiniclUhys,  etc.)  and  of  the  ganoids  of  the  Upper 
Devonian  of  Scotland,  the  establishment  of  all  the 
great  modern  orders  of  fishes  excepting  the  bony 
fishes  (Teleosts),  and  the  appearance  of  the  first 
land  vertebrates,  the  amphibians  {Thinopus)^ 
took  place  during  this  period  of  depression  of  the 
western  centre  of  the  North  American  continent. 
Modified  after  Schuchert. 


i 


176  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

producing  organs  in  the  fishes  themselves  and  in  other  animals 

on  which  they  prey.  .      r  u      • 

Another  extreme  of  chemical  evolution  among  the  fishes  is 
the  production  of  electricity  as  a  protective  function,  which  is 

even  more  effective  than  bony  arma- 
ture because  it  does  not  interfere  with 
rapid  locomotion.     In  only  a  few  of 
the   fishes   is   electricity   generated   in 
sufficient  amounts  to  thoroughly  pro- 
tect the  organism.     It  develops  through 
modified  body  tissues  in  the  form  of 
superimposed  plates  (electroplaxes)  se- 
parated equally  from  one  another  by 
layers  of  a  peculiar  jelly-like  connec- 
tive tissue,  all  lying  parallel  to  each 
other  and  at  right  angles  to  the  direc- 
tion of  discharge.!     The  electric  organ 
is  formed  from  modified  muscle  and 
connective  tissue  and  is  innervated  by 
motor  nerves.     The  physical  principle 
involved  is  that  of  the  concentration 
cell,  and  the  electrolyte  used  in  the 
process  is  probably   sodium   chloride. 
The  theory  is  that  at  the  moment  of 
discharge  a  membrane  is  formed  on  one 
surface  of  the  electroplax  which  prevents  the  negative  ions 
from  passing  through  while  the  positive  ions  do  pass  through 
and  form  the  current.     The  strength  of   the  current  varies 
from  four  volts  in  Mormyrus  up  to  as  much  as  250  or  more 
in  Gymnotus,  the  electric  eel,  and  consists  of  a  series  of  shocks 
discharged  3/1000  of  a  second  apart. 

1  Dahlgrcn,  Ulric,  1906,  pp.  389-398;   iQio,  P-  200. 


EVOLUTION  OF  THE  AMPHIBIANS 


177 


Fig.   57.    The   Earliest 
Known  Limbed  Animal. 
Footprint   of    Thinopus    anti- 
qiius  Marsh,  an  amphibian 
from  the  Upper  Devonian  of 
Pennsylvania.     Type  in  the 
Peabody   Museum   of   Yale 
University.      Photograph  of 
cast  presented  to  the  Ameri- 
can Museum  of  Natural  His- 
tory     by      the      Peabody 
Museum. 


^ 


Form  Evolution  of  the  Amphibians 

A  single  impression  of  a  three-toed  footprint  {Thinopus 
antiquus)  in  the  Upper  Devonian  shales  of  Pennsylvania  con- 
stitutes at  present  the  sole  palaeontologic  proof  of  the  long 
period  of  transition  of  the  vertebrates  from  the  fish  type  to 
the  amphibian  type.  This  transition  was  a  matter  of  thousands 
of  years.  It  took  place  in  Lower  Devonian  if  not  in  Upper 
Silurian  time.  Under  the 
influence  of  the  heredity- 
chromatin  it  is  now  re- 
hearsed or  recapitulated  in 
a  few  days  in  the  metamor- 
phosis from  the  tadpole  to 
the  frog. 

As  compared  with 
fishes,  the  significant  prin- 
ciple of  the  evolution  of 
amphibians,  as  the  earliest  terrestrial  vertebrates,  is  their  reac- 
tion to  marked  environmental  change.  Their  entire  life  re- 
sponds to  the  changes  of  the  seasons.  They  also  respond  to 
secular  changes  of  environment  in  the  evolution  of  types 
adapted  to  extremely  arid  conditions. 

The  adaptive  radiation  of  the  primordial  Amphibia  prob- 
ably began  in  Middle  Devonian  time  and  extended  through 
the  great  swamp,  coal-forming  period  of  the  Carboniferous, 
which  afforded  over  vast  areas  of  the  earth's  surface  ideal  con- 
ditions for  amphibian  evolution,  the  stages  of  which  are  best 
preserved  in  the  Coal  Measures  of  Scotland,  Saxony,  Bohemia, 
Ohio,  and  Pennsylvania,  and  have  been  revealed  through  the 
studies  of  von  Meyer,  Owen,  Fritsch,  Cope,  Credner,  and 
Moodie.     The  earliest  of  these  terrestrio-aquatic  types  have 


Fig.  58.    A  Primitive  Amphibian. 

Theoretic  reconstruction  of  a  primitive  sala- 
mander-like type  with  large,  solidly  roofed 
skull,  four  limbs,  and  five  fingers  on  each  of 
the  fore  and  hind  feet,  such  as  may  have  ex- 
isted in  Upper  Devonian  time.    After  Fritsch. 


178  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

not  only  a  dual  breathing  system  of  gills  and  lungs,  but  a  dual 
motor  equipment  of  limbs  and  of  a  propelling  median  fin  m 

the  tail  region. 

So  far  as  known,  the  primordial  Amphibia  in  their  form  were 
chiefly  of  the  small-headed,  long-bodied,  small-limbed,  tail-pro- 


ORIGIN  AND  ADAFTIVt  RADIATION  OF  TMCAMPHWIA 


Fig  59.  Descent  of  the  Amphibia 
The  Amphibia-in  which  the  fin  is  transformed  into  a  limb  {Thuwpus)-^TC  believed  to 
have  evolved  from  an  ancestral  ganoid  fish  stock  of  Silurian  age  through  the  frmge- 
finned  ganoids.  From  this  group  diverge  the  ancestors  of  the  Reptilia  and  the  sala- 
mander-like Amphibia  which  give  rise  to  the  various  salamander  types,  also  to  branches 
of  limbless  and  snake-like  forms  (Aistopoda,  modem  Coecilians).  The  other  great 
branch  of  the  solid-skulled  Amphibia,  the  Stegocephalia,  was  widespread  all  over  the 
northern  continents  in  Permian  and  Triassic  time  {Cricolus,  Eryops).  and  from  this 
stock  descended  the  modern  frogs  and  toads  (.\nura).  Prepared  for  the  author  by 
W.  K.  Gregory. 

pelled  type  of  the  modern  salamander  and  newt.  The  large- 
headed,  short-bodied  types  {Amphihamus)  were  precocious 
descendants  of  such  primordial  forms.     In  Upper  Carbonifer- 


EVOLUTION  OF  THE  AMPHIBIANS 


179 


, 


ous  and  early  Permian  time  the  terrestrial  amphibians  began 
to  be  favored  by  the  land  elevation  and  recession  of  the  sea 
which  distinguished  the  close  of  the  Carboniferous  and  early 
Permian  time.  Under  these  varied  zonal  conditions,  aquatic, 
palustral,  terrestrio-aquatic,  fossorial,  and  terrestrial,  the  Am- 


EUMICRERPETON 
AMPHIBIA  CARBONIFEROUS 


PTYONIUS 


AMPHIBIA 


CARBONIFEROUS^ 


AMPHIBAMUS 
AMPHIBIA  CARBONIFEROUS 


DIPLOCAULUS 


AMPHIBIA 


PERMO- 
CARBONIFEROUS 


Fig.  60.    Chief  Amphibian  Types  of  the  Carboniferous. 
Restorations  of  the  early  short-tailed,  land-living  Amphibamus,   the  salamander-like 
Eumkrerpelofi,  the  eel-bodied  Plyonius,  and  the  broad-headed,  bottom-livmg  Diplo- 
caiilus.     Prepared  for  the  author  by  W.  K.  Gregory  and  Richard  Deckert. 

phibia  began  to  radiate  into  several  habitat  zones  and  adaptive 
phases,  and  thus  to  imitate  the  chief  types  of  body  form  which 
had  previously  evolved  among  the  fishes  as  well  as  to  anticipate 
many  of  the  types  of  body  form  which  were  to  evolve  subse- 
quently among  the  reptiles.  One  ancestral  feature  of  the 
amphibians  is  a  layer  of  superficial  body  scales  in  some  types, 
which  appear  to  be  derived  from  those  of  their  lobe-finned  fish 
ancestors;  with  the  loss  of  these  scales  most  of  the  Amphibia 
also  lost  the  power  of  forming  a  bony  dermal  armature. 


i8o  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

Recent  researches  in  this  country,  chiefly  by  Williston, 
Case  and  Moodie,  indicate  that  the  solid-headed  Amphibia 
(Stegocephalia)  and  primary  forms  of  the  Reptilia  chiefly  be- 
long to  late  Carboniferous  (Pennsylvania)  and  early  Permian 
time  They  are  found  abundantly  in  ancient  pool  deposits, 
which  are  now  widespread  over  the  southwestern  United  States 

and  Europe  deposited  in 
rocks  of  a  reddish  color. 
This  reddish  color  points 
to  aridity  of  climate  in 
the  northern    hemis- 
phere during  the  period 
in  which  the  terrestrial 
adaptive  radiation  of  the 
Amphibia  occurred. 
These  arid  conditions 
continued    during    the 
greater  part  of  Permian 
time,   especially   in   the 
northern  hemisphere. 
In  the  southern  hemisphere  there  is  evidence,  on  ^he  con- 
trary, of  a  period  of  humidity,  cold,  and  extensive  glaciaticn, 
which  was  accompanied  by  the  disappearance  of  the  old  lyco- 
pod  flora  (club-mosses)  and  arrival  of  the  cool  fern  flora  {Glos- 
sopteris),  which  appeared  simultaneously  in  South  America, 
South  Africa,  Australia,  Tasmania,  and  southern  India.     The 
widespread  distribution  of  this  flora  in  the  southern  hemisphere 
furnishes  one  of  the  arguments  for  the  existence  of  the  great 
South  Atlantic  continent  Gondumia,  a  transatlantic  land  bridge 
of  animal  and  plant  migration,  postulated  by  Suess  and  sup- 
ported   by    the    palffiogeographic    studies    of    Schuchert.     In 
North  America  the  glaciation  of  Permian  time  is  believed  to 


EVOLUTION  OF  THE  AMPHIBIANS 


i8i 


Fig.  6i. 


Skull  and  Vertebral  Column  of 
Diplocaiilns. 

A  typical  solid-,  broad-headed  amphibian  from  the 
Permian  of  northern  Texas.  Specimen  m  the 
American  Museum  of  Natural  History.  (Com- 
pare Fig.  60.) 


.*> 


♦ 


'' 


have  been  only  local.  The  last  of  the  great  Palaeozoic  seas  dis- 
appeared from  the  surface  of  the  continents,  while  the  border 
seas  give  evidence  of  the  rise  of  the  ammonite  cephalopods. 
Toward  the  close  of  Permian  time  the  continent  was  com- 
pletely drained.     Along  the  eastern  seaboard  the  Appalachian 


EARLIEST 
PERMIAN 


L 


r*LEOCEOGRAPHV.  EARLIEST  PERMIAN  <LOWER  ARTINSKIAN-HOTLIEGENDE-AUTUNIAN).  A  GLACIAL  TIME 

AFTER  SCMUCHeBT.  APRIL.  1»1» 
^  .    ...    ruToneiTQ  A» ICE  FIELDS  t   OtnECTION  OF  ICE  FLOW 


Fig.  62.    Theoretic  World  Environment  in  Earliest  Permian  Time. 
\  period  of  marked  glacial  conditions  in  the  Antarctic  region.     Vanishing  of  the  coal 
floras  and  rise  of  the  cycad-conifer  floras,  along  with  the  rise  of  more  modern  insects  and 
the  beginning  of  the  dominance  of  reptiles.     Modified  after  Schuchert,  1916. 

revolution  occurred,  and  the  mountains  rose  to  heights  esti- 
mated at  from  three  to  five  miles. 

An  opposite  extreme,  of  slender  body  structure,  is  found 
in  the  active  predaceous  types  of  water-loving  amphibians  such 
as  Cricotus,  of  rapid  movements,  propelled  by  a  long  tail  fin, 
and  with  sharp  teeth  adapted  to  seizing  an  actively  moving 
prey.  This  type  retrogresses  into  the  eel-like,  bottom-loving 
Lysorophus  with  its  slender  skull,  elongate  body  propelled  by 


i82  THE  ORIGIN  AND  EVOLUTION   OF  LIFE 

lateral  swimming  undulations,  the  limbs  relatively  useless. 
Corresponding  to  the  bottom-living  fishes  are  the  large,  slug- 
gish, broad-headed,  bottom-living  amphibians,  such  as  Diplo- 
caulus,  with  heads  heavily  armored,  limbs  small  and  weak,  the 
body  propelled  by  lateral  motions  of  the  tail.     There  were  also 


>U4PHIB1A 


CWCOTUS  PEWMO- 

CAABONIFEROUS 


PERMO~ 
AMPHIBIA  CACOPS  CARBONIFEROUS 


AMPHIBIA 


ERVOPS 


PCRMO- 

CARBONIFEROUS 


Fig.  63.    Amphibia  of  the  .\merican  Permo-Carboniferous. 
Here  are  found  the  free-swimming  Cricolus,  the  short-bodied  Cacops    and  abundance  of 
the  amphibious  terrestrial  type  the  large,  solid-headed  Eryops.    Restorations  for  the 
author  by  W.  K.  Gregory  and  Richard  Deckert. 

more  powerful,  slow-moving,  long-headed,  alligator-like,  terres- 
trio-aquatic  forms,  such  as  the  Archegosaurus  of  Europe  and 
the  fully  aquatic  Trimerorachis  of  America.  An  extreme 
stage  of  terrestrial,  ground-living  evolution  with  marked  reduc- 
tion of  the  use  of  the  tail  for  propulsion  is  the  large-headed 
Cacops,  short-bodied,  with  limbs  of  medium  size,  but  with 
feeble  powers  of  prehension  in  the  feet.  Radiating  around 
these  animals  were  a  number  of  terrestrial  types  exhibiting 
the  evolution  of  dorsal  protective  armature  and  spines  {Aspi- 
dosaurus) ;  other  types  lead  into  the  pointed-headed  structure 
and  pointed  teeth  of  Trematops. 


EVOLUTION  OF  THE  AMPHIBIANS 


183 


The  Age  of  Amphibians  passes  its  climax  in  Permian  time 
(Fig  63.).  In  Triassic  time  there  still  survive  the  giant  terres- 
trial forms. 

Evidences  of  extensive  intercontinental  connections  in  the 
northern  hemisphere  are  also  found  in  the  similarity  of  type 
between  the  great  terrestrial  amphibians  of  such  widely  sepa- 
rated areas  as  Texas  and  Wiirtemberg,  which  develop  into  simi- 
lar resemblances  between  the  great  labyrinthodont  amphibians 
of  Lower  Triassic  times  of  Europe,  North  America,  and  Africa. 
Ancestral  to  these  Triassic  giants  is  the  large,  sluggish,  water- 
and  shore-living  Eryops  of  the  Texas  Permian,  with  massive 
head,  depending  on  its  short,  powerful  limbs  and  broad,  spread- 
ing feet  for  land  propulsion,  and  in  a  less  degree  upon  its  tail  for 
propulsion  in  the  water.     This  animal  may  be  regarded  as  a 
collateral  ancestor  of  the  labyrinthodonts;  it  belongs  to  a  type 
which  spread  all  over  Europe  and  North  America  and  persisted 
into  the  Metopias  of  the  Triassic. 


fc_:^-,«j>»-I-^.-  M.  •«»«>*•>■'•■ 


1  IG     04.      SKELETON   OF  Eryops   FROM  THE    PeRMO-CaRBONIFEROUS   OF   TEXAS. 

A  tvne  of  the  stegocephalian  Amphibia  which  were  structurally  ancestral  to  the  Laby- 
r^nthodonts  of  the  Triassic.     Mounted  in  the  American  Museum  of  Natural  History. 


CHAPTER  VII 
FORM  EVOLUTION  OF  THE  REPTILES  AND  BIRDS 

Appearance  of  earliest  reptile-like  forms,  the  pro-Reptilia,  followed  by  the  first 
higher  reptiles.  Geologic  distribution  and  environment  of  the  various 
extinct  and  existing  orders  of  reptilia.  Evolutionary  laws  exemplified  in 
the  origin  and  development  of  this  great  group  of  animal  life.  Direct, 
reversed,  alternate,  and  convergent  adaptation.  Modes  of  offense  and 
defense.  Terrestrial,  fossorial,  aquatic,  and  marine  radiation.  Aerial 
adaptation.  The  Pterosaurs.  First  appearance  of  bird-like  animals. 
Theories  regarding  the  evolution  of  flight  in  birds.  Theories  as  to  the 
causes  of  arrested  evolution. 

The  environment  of  the  ancestor  of  all  the  reptiles  was  a 
warm,  terrestrial,  and  semi-arid  region,  favorable  to  a  sensitive 
nervous  system,  alert  motions,  scaly  armature,  slender  limbs, 
a  vibratile  tail,  and  the  capture  of  food  both  by  sharply  pointed, 
recurved  teeth  and  by  the  claws  of  a  five-fingered  hand  and 
foot.  The  mechanically  adaptive  evolution  of  the  Reptilia 
from  such  an  ancestor  is  as  marvellous  and  extreme  as  the 
subsequent  evolution  of  the  mammals;  it  far  exceeds  in  di- 
versity the  radiation  of  the  Amphibia  and  extends  over  a  pe- 
riod estimated  at  from  15,000,000  to  20,000,000  years. 

The   Permian   Reptiles   of   North   America   and   South 

Africa 

The  experiments  of  the  Amphibia  in  adapting  themselves 
to  the  Permian  continents  with  their  relatively  dry  surfaces 
and  seasonal  water  pools  and  lagoons  are  contemporaneous 
with  the  first  terrestrial  experiments  and  adaptive  radiations 
of  the  ReptiUa,  a  group  which  was  particularly  favored  in  its 

184 


EARLIEST  REPTILES 


185 


origin  by  arid  environmental  conditions.  The  result  is  the 
creation  in  Permian  time  of  many  externally  analogous  or  con- 
vergent groups  of  amphibians  and  reptiles  which  in  external 
appearance  are  difficult  to  distinguish.  Yet  as  divergent  from 
the  primitive  salamander-like  Amphibia  and  clearly  of  another 


«U*0«0«l*««t.  t*BUtST  PERM.AN  (LOWER  .BT.NSK.AN.BOTUEGENOE-AUTUN.AN,.  A  GL^.AL  T.ME 

AFTER  SCHOCHERT.  AWIU  1»1» 

,  „         ifeiCE  riELDS  t   DIRECTION  Of  ICE  FLOW 

^  cncDMira         ♦continental  DEPOSITS         lF^/'^'-~  „.„, 

t  ''*""*^  ""^UHWITAm  ICE  FIELDS  .--VOLCANOES         .»»■ 


«  MOUNTAINS 


Fig   65     Theoretic  World  Enxtronment  in  Earliest  Permian  Time. 
a^the  bcgX  of  the  dominance  of  reptiles.     Modified  after  Schuchert,  ^,^6. 

type  these  pro-reptiles  are  different  in  the  inner  skeletal  struc- 
ture and  in  the  anatomy  of  the  skull  they  are  exclusively 
air-breathing,  primarily  terrestrial  in  habit  rather  than  ter- 
restrio-aquatic,  superior  in  their  nervous  reactions  and  in  the 
development  of  all  the  sensory  organs,  and  have  a  more 
highly  perfected  cold-blooded  circulatory  system.  Neverthe- 
less the  most  ancient  solid-headed  reptilian  skull  type  (Cotylo- 
sauria   Pareiasauria,  of  Texas  and  South  Africa,  respectively) 


i86 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


REPTIUA 


VARANOPS 


PERMO- 
CARBONIFEROUS 


ARAEOSCELIS 


PEPTILIA 


PERMO 
CARBONIFEROUS 


is  very  similar  to  that  of  the  soUd-headed  Amphibia  (Steg- 
ocephalia).     Bone  by  bone  its  parts  indicate  a  common  descent 

from  the  skull  type  of  the  fringe- 
finned    fishes    (Crossopterygia, 

Fig-  S3)- 

As  revealed  by  the  researches 

of  Cope,   Williston,   and   Case, 
the   adaptive   radiation   of   the 
reptile  life  of  western  America 
in  Permian  time  is  as  follows: 
First  there  is  a  variety  of  swift- 
moving,  alert,  predaceous  forms 
corresponding  to  the  fusiform, 
swift-moving  stage  in  the  evolu- 
tion   of    the    fishes.     Some    of 
these    reptiles    (Varanops)    re- 
semble the  modern  monitor  liz- 
ards (Varaniis)]    others  (Ophi' 
acodon    and     Theroplcura)    are 
provided  with  four  well-devel- 
oped limbs  and  feet,  the  long  tail 
being    utilized    as    a  balancing 
organ.     These  were  littoral  or 
lowland   reptiles,    insectivorous 
or  carnivorous   in  habit.     The 
primitive,   lizard-like  pelycosaur   Varanops,  with  a  long   tail 
and  four  limbs  of  equal  proportions,  represents  more  nearly 
than  any  know^n  ancient  reptile,  apart  from  certain  special 
characters,  a  generalized  prototype  from  which  all  the  eighteen 
Orders  of  the  Reptilia  might  have  descended;  its  structure  could 
well  be  ancestral  to  that  of  the  lizards,  the  alligators,  and  the 
dinosaurs.     At  present,  however,  it  is  not  determined  whether 


Fig.  66.    Ancestral  Reptilian  Types. 

Two  of  the  defenseless,  swift-moving, 
terrestrial  reptilian  types,  Varanops 
and  ArcBoscelis,  of  the  Permo-Carbonif- 
erous  period  of  Texas.  The  skull  and 
skeleton  of  ArcBOscelis  foreshadow  the 
existing  lizard  (Lacertilian)  type  and 
Williston  regards  it  as  the  most  nearly 
related  Permian  representative  known 
of  the  true  Squamata  (ancestors  of 
the  lizards,  snakes,  and  mosasaurs). 
Restorations  of  Varanops  and  Araos- 
celis  modified  from  Williston.  Drawn 
for  the  author  by  Richard  Deckert. 


EARLIEST  REPTILES 


187 


REPTILIA 


PERMO- 
CARBONIFEROUS 


REPTILIA 


SEYMOURIA 


PERMO- 
CARBONIFEROUS 


mt^r.-rfjiK, 


the  primitive  ancestors  from  which  the  various  orders  of  reptiles 
descended  belong  to  a  single,  a  double,  or  a  multiple  stock. 

Passing  to  the  widely  different  amphibian-like  order  known 
as  cotylosaurs,  we  see  animals 
which,  on  the  one  hand,  grade 
into  the  more  fully  aquatic,  pad- 
dle-footed, free-swimming  Lim- 
noscclis  with  a  short,  crocodile- 
like head,  which  propelled  itself 
by  means  of  its  long  tail,  and,  ^^^^^ 
on  the  other  hand,  there  devel- 
oped short-tailed,  semi-aquatic 
forms,    such    as     the     Labido- 
sauriis.      In  adaptation  to  the 
more  purely  terrestrial  habitats 
there  is  sometimes  a  reduction 
in  the  length  of   the   tail   and 
greater  perfection  in  the  struc- 
ture of  the  limbs  and  the  various 
forms  of  armature.     In  Pantylus 
these    defenses    appear   in    the 
form  of  bony  ossicles  of  the  skin 
and    scutes;     in    Chilonyx    the 
skull  top  is  covered  with  tuber- 
culated  defenses;    in  the  slow- 
moving   Diadedes   the  body  is 
partly  armored,  the  animal  be- 
ing proportioned  like  the  exist- 
ing Gila  monster  and  probably 
of  nocturnal  habits,  w^hich  is  in- 
ferred from  the  large  size  of  the 
eyes. 


REPTILIA 


DIADECTES 


PERMO- 
CARBONlFEROUS 


Fig.  67.  Reptiles  with  Skulls  Trans- 
itional IN  Structure  from  the 
Amphibian  Skull. 

Typical     solid-headed     reptiles     (Coty- 
losaurs)   characteristic   of   Permo-Car- 
boniferous    time    in    northern    Texas, 
including  the  three  forms  Scymouria, 
Labidosauriis,  and  the  powerful  Dia- 
dedes,   which    resembles    the   existmg 
Gila  monster.  The  head  in  the  mounted 
skeleton   of   Diadedes    (lower)    in   the 
American  Museum  of  Natural  History 
is  probably  bent  too  sharply  on  the 
neck.     Restorations  for  thi  author  by 
W.  K.  Gregorys  and  Ev.hard  Deckert. 
Labidosauriis    and    Seymouna    diiefly 
after  Williston. 


i88 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


The  most  remarkable  types  in  this  complex  reptilian  society 
of  Permian  Texas  are  the  giant  fin-backed  lizards,  Clcpsydrops, 
Dimetrodon,  Edaphosaurus,  of  Cope,  probably  terrestrial  and 
carnivorous  in  habit.  In  these  animals  the  neural  spines  of 
the  dorsal  vertebrae  are  vertically  elongated  to  support  a  power- 
ful median  membranous  fin,  the  spines  of  which  are  sometimes 


X'MABINE  DEPOSITS 


PALEOGEOCRAPHY.  MIDDLE  PERMIAN  (THuniNGIAN-ZECHSTEIN)  TIMC 

I  AFTER  SCHUCHtRT.  APRIL.  1»1« 

^k.  COHTIHEMTAL  DEPOSITS  Jt  GYPSUM  AMO  SALT 


MOUNTAINS  V   OONOWANA  FLOMA 


Fig.  68,    Theoretic  World  Environment  in  Middle  Permian  Time. 

Great  extension  of  the  Baltic  Sea  and  of  the  Eurasiatic  Mediterranean  Telhys.  Rise  of 
the  Appalachian,  Northern  European  Alps,  and  many  other  mountains.  Modified 
after  Schuchert. 

smooth  (Dimetrodon) ,  sometimes  provided  with  transverse  rods 
{Edaphosaurus  cruciger).  These  structures  may  have  devel- 
oped through  social  or  racial  competition  and  selection  within 
this  reptile  family  rather  than  as  offensive  or  defensive  organs 
in  relation  to  other  reptile  families. 

We  now  glance  at  the  Permian  life  of  another  great  zoologic 
region.  Africa  has  been  throughout  all  geologic  time  the 
most    stable    of    the    continents,    especially    since   the   begin- 


EARLIEST  REPTILES 


189 


ning  of  the  Permian  Epoch. 
The  contemporaneous  evo- 
lution  of   the  pro-Reptilia, 
traced  in  a  continuous  earth 
section  from  the  base  of  the 
Permian  to  the  Lower  Trias- 
sic,  as  successively  explored 
by     Bain,     Owen,     Seeley, 
Broom,  and  Watson,  has  re- 
vealed a  far  more  extensive 
and   more   varied   adaptive 
radiation  of  the  reptiles  than 
that  which  is  known  on  the 
American  continent.     Al- 
though the  adaptations  are 
chiefly  terrestrial,  we  trace 
certain   strong   analogies   if 
not  actual  relationships  to 
the  Permo-Triassic  reptiles 
of  North  America. 

While  the  drying  pools 
and  lagoons  of  arid  North 
America  were  entombing  the 
life    of    the    Permian    and 
Triassic  Epochs,  there  were 
being  deposited  in  the  Karoo 
series  of  South  Africa  some 
9,500  feet  of  strata  consist- 
ing of  shales  and  sandstones, 
chiefly   of   river  flood-plain 
and  delta  origin,  and  rang- 
ing in  time  from  the  basal 


mi     - 


«S**W-rt!.?:'<- 


tOAPHOSAURUS 


REPTIUA 


PERMO- 
CARBONIFEROUS 


OIMETTROIXJN 


REPTIUA 


PERMO- 
CARBONIFEROUS 


Fig.  69.    The  Fin-Back  Permian 
Reptiles. 

Restorations  (middle  and  upper  figures)  of 
the  giant  carnivorous  reptiles  of  northern 
Texas  in  Permian  time;  the  large-headed 
Dhnetrodon  and  the  contemporary  small- 
headed  Edaphosaurus  cmciger.  In  both 
animals  the  neural  spines  of  the  vertebrae 
are  greatly  elongated,  hence  the  popular 
name  "fin-back."  Skeleton  of  Dimetrodon 
(lower)  in  the  American  Museum  of  Natural 
History.  Restorations  for  the  author  by 
W.  K.  Gregory  and  Richard  Deckert. 


I    1; 

1 1    f" 


REPTIUA 


ENDOTHIODON 


PCRMIAN 


k:tido»>sis 


HEPTILIA 


TRIASSIC 


190  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

Permian  into  the  Upper  Triassic.  Here,  up  to  the  year  1909, 
twenty-two  species  of  fossil  fishes  had  been  recorded,  mostly 
ganoids  of  Triassic  age.  The  eleven  species  of  amphibians  dis- 
covered are  of  the  solid-headed  (Stegocephalia)  t}ipe,  broadly 

similar  in  external  appearance  to 
those  of  the  same  age  discovered 
in  Europe.     The  one  hundred  and 
fifteen  species  of  reptiles  described 
from  the  Lower  and  Middle  Per- 
mian deposits  include  solid-headed 
pareiasaurs — great,  round-bodied, 
herbivorous  reptiles  with  massive 
limbs  and  round  heads — which  are 
allied   to  the  cotylosaurs   of   the 
Permo-Carboniferous  of  America, 
the  agile  dromosaurs,  similar  to  the 
lizard-like   reptiles   of   the   Texas 
Permian,  with  large  eye-sockets, 
and    adapted    to    swift,    cursorial 
movements,   also   reptiles   known 
as  therocephaUans  in  reference  to 
the  analogy  which  the  skull  bears 
to  that  of  the  mammals,  gorganop- 
sians,  and  numerous  slender- 
limbed,    predatory    reptiles    with 
sharp  caniniform  teeth.    The  giant 
predaceous  Reptilia  of  the  time 
are  the  dinocephalians  {i.  e./'  terri- 
ble-headed ") ,  very  massive  animals  with  a  highly  arched  back, 
broad,  swollen  forehead,  short,  wide  jaws  provided  with  mar- 
ginal teeth.     Surpassing  these  in  size  are  the  anomodonts  (z.  e., 
-lawless-toothed")  in  which  the  skull  ranges  from   a  couple 


RCPTILIA 


CYI40CNATHUS 


TRIASSIC 


Fig.  70.    Mammal-like  Reptiij:s  of 
South  Africa. 

The  relative  stability  of  the  African 
continent  favored  the  early  evolu- 
tion  of  the   free-limbed    forms   of 
reptiles  known  as  Anomodonts,  in- 
cluding the  powerful  Endothiodon, 
in  which  the  jaws  are  sheathed  in 
horn  like  those  of  turtles;   and  also 
of     the     Cynodonts     (dog-toothed 
reptiles),  including  the  carnivorous, 
strongly  toothed  Cynognathus  which 
is   allied   to   the   ancestors   of   the 
Mammalia.     Restorations   for   the 
author    by    W.    K.    Gregory    and 
Richard  Deckert. 


MAMMAL-LIKE   REPTILES 


191 


of  inches  to  a  yard  in  length,  and  the  toothless  jaws  are  sheathed 
in  horn  and  beaked  like  those  of  turtles.  This  is  a  nearly 
typical  social  group:  large  and  small,  herbivorous,  omnivorous, 
and  carnivorous,  toothed,  toothless  and  horny-beaked,  swift- 
moving,  slow-moving,  unarmored,  partly  armored;  it  lacks 
only  the  completely  armored,  slow-moving  type  to  be  a  perfect 

complex. 

In  the  Upper  Permian  the  fauna  includes  pareiasaurs  and 
gorganopsians,  which  are  similar  to  a  large  group  of  reptiles  of 
the  same  geologic  age  discovered  in  Russia  by  Amalitzky. 

In  Lower  and  Middle  Triassic  time  the  last  and  most  highly 
specialized  of  the  beaked  anomodonts  appear  together  with  di- 
minished survivors  {ProcolopJwn)  of  the  very  ancient  solid-headed 
order  (Pareiasauria  of  South  Africa,  Cotylosauria  of  Texas). 
Here  also  are  found  the  true  cynodonts,  which  are  the  most 
mammal-like  of  all  known  reptiles.  In  the  Upper  Triassic  of 
South  Africa  occur  carnivorous  dinosaurs,  also  crocodile-like  phy- 
tosaurs  (Fig.  75),  allied  to  those  of  Europe  and  North  America. 

Origin  of  the  Mammals  and  Adaptive  Radiation  of  the 

Eighteen  Orders  of  Reptiles 

The  most  notable  element  in  this  complex  reptilian  society 
of  South  Africa  are  those  remarkable  pro-mammalian  types  of 
reptiles  (cynodont,  theriodont),  from  which  our  own  most 
remote  ancestors,  the  stem  forms  of  the  Mammalia,  the  next 
higher  class  of  vertebrates  above  the  Reptilia,  were  destined  to 
arise.  This  is  another  instance  where  palaeontology  has  dis- 
lodged a  descent  theory  based  upon  anatomy,  for  at  one  time 
from  anatomical  evidence  alone  Huxley  was  disposed  to  derive 
the  mammals  directly  from  the  amphibians. 

The  question  at  once  arises,  why  were  these  particular  reptiles 
so  highly  favored  as  to  become  the  potential  ancestors  of  the 


SCYMNOGNATHUS 


REPnUA 


PERMIAN 


192  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

mammals?    At  least  two  reasons  are  apparent.     First,  these 
1    gTand  smaller  types  of  South  African  P— ^^^^^  ^^^^^ 
an  exceptional  evolution  of  the  four  limbs,  e-blmg  them    o 
travel  with  relative  rapidity,  which  is  connected  with  abihty 
to  milte    powers  doubtless  associated  with  mcreasmg   m- 
llirnce       Lother  marked  characteristic  which  favors   de- 
vZ-nt  of  intelligence  is  the  adaptability  of  the.  teeth  t 
different  kinds  of  food,  insectivorous,  carnivorous   and  herbiv 

orous,  which  leads  to  development  and 
diversity  of  the  powers  of  observation 
and  choice.     In  this  adaptability  they 
in  a  limited  degree  anticipate  the  evo- 
lution of  the  mammals,  for  the  other 
reptiles  generally  are  distinguished  by  a 
singular  arrest  or  inertia  in  tooth  de- 
velopment.  Rapid  specialization  of  the 
teeth  is  one  of  the  chief  features  in  the 
history  of  the  mammals,  which  display 
a  continuous  momentum  and  advance 
in    tooth    structure,    associated    with 
specialization  of  the  organs  of  taste. 
Of  greater  importance  in  its  influence   on   the  brain  evolu- 
Uon  of  the  early  pro-mammaUan  forms  is  the  mternal  tem- 
Tature    change,    whereby    a    -M-blooded,    scaly    rept.es 
transformed  into  a  warm-blooded  mammal  through  a  change 
:  S  pluced  the  four-chambered  heart  and  comp  ete  .p- 

aration  of  the  arterial  and  venous  --^^^--^ J^^^^^f^ 
may  have  been  initiated  in  some  of  the  cynodonts.    This  new 
Tstant  and  higher  temperature  favors  the  --us  ^lutio 
of  the  mammals  but  has  no  influence  whatever  upon  the  me 
lanical  evolution.     As  pure  mechanisms  the  ^o^'^^^^^^^ 
tiles  exhibit  as  great  plasticity,  as  great  diversity,  and  perhaps 


ADAPTIVE  RADIATION  OF  REPTILES 


193 


Fig.    7^ 


A  South  African 
"Dog-Toothed"  Reptile. 

Head  of  one  of  the  South 
African  Cynodonts  or  "dog- 
toothed"  reptiles,  related  to 
the  ancestors  of  the  mam- 
mals. Restoration  for  the 
author  by  W.  K.  Gregory 
and  Richard  Deckert. 


higher  stages  of  perfection  than  the  mammals.    Nor  does  increas- 
ing intelligence,  as  we  shall  see,  favor  mechanical  perfection. 

Turning  our  survey  to  the  origin  and  adaptive  radiation  of 
the  reptiles  as  a  whole,  we  find  that  in  Permian  time  all  of  the 


ORIGIN  AND  ADAPTIVE  RADIATION  Of  THE  REPTILES 


w.  iL  UKGorr,  (III 


Fig.  72.  Adaptive  Radiation  of  the  Reptilia. 
The  reptiles  first  appear  in  Upper  Carboniferous  and  Lower  Permian  time  and  radiate  into 
eighteen  different  orders,  three  of  which— the  Cotylosaurs,  Anomodonts,  and  Pely- 
cosaurs— attain  their  full  evolution  in  Permian  and  Triassic  time  and  later  become 
extinct.  Six  orders— the  Ichthyosaurs,  Plesiosaurs,  Dinosaurs,  Phytosaurs,  Pterosaurs, 
and  Turtles— are  first  discovered  in  Triassic  time,  while  five  of  the  orders— the  Ich- 
thyosaurs, Plesiosaurs,  Mosasaurs,  Dinosaurs,  and  Pterosaurs— dominate  the  Cretace- 
ous Period  and  become  suddenly  extinct  at  its  close,  leaving  the  five  surviving  modern 
orders- Testudinata  (turtles,  tortoises),  Rhyncocephalia  (tuateras),  Lacertilia  (lizards), 
Ophidia  (snakes),  and  Crocodilia  (crocodiles).  These  great  reptilian  dynasties  seem 
to  have  extended  over  the  estimated  ten  million  years  of  the  IMesozoic  Era,  namely,  the 
Triassic,  Jurassic,  and  Upper  Cretaceous  Epochs.  Prepared  for  the  author  by  W.  K. 
Gregory. 

ten  early  adaptive  branches  of  the  reptilian  stem  had  radiated 
and  become  established  as  prototypes  and  ancestors  of  the 
great  Mesozoic  Reptilia.  Five  divisions,  namely,  the  coty- 
losaurs, anomodonts,  pelycosaurs,  proganosaurs,  and  phyto- 
saurs, were  destined  to  become  extinct  in  Permian  or  Triassic 
time,  in  each  instance  as  the  penalty  of  excessive  and  prema- 


194  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

ture  specialization.  Five  other  great  branches,  namely,  the 
ichthyosaurs,  plesiosaurs,  two  great  branches  of  the  dinosaurs, 
and  the  pterosaurs,  were  destined  to  dominate  the  waters, 
the  earth,  and  the  air  during  the  Mesozoic  Era,  i,  e.,  the  Tri- 
assic,  Jurassic,  and  Cretaceous  Epochs.  Thus  altogether  thir- 
teen great  branches  of  the  reptilian  stock  became  extinct  either 
before  or  near  the  close  of  the  Age  of  Reptiles.  Out  of  the 
total  of  eighteen  reptilian  branches  only  five  were  destined  to 
survive  into  Tertiary  time,  namely,  the  orders  which  include 
the  existing  turtles,  tuateras,  lizards,  snakes,  and  crocodiles. 

Geologic  Blanks  and  Vistas  of  Reptilian  Evolution 
As  pointed  out  in  the  introduction  of  this  chapter,  the  rep- 
tile ancestor  of  these  eighteen  branches  of  the  class  Reptilia 
a  class  with  an  adaptive  radiation  which  represents  the  mechan- 
ical conquest  of  every  one  of  the  great  life  zones,  from  the  aerial 
to  the  deep  sea — will  some  day  be  discovered  as  a  small,  lizard- 
like, cold-blooded,  egg-laying,  four-limbed,  long-tailed  terres- 
trial form,  with  a  solid  skull  roof,  of  carnivorous  or  more  prob- 
ably insectivorous  habit,  which  lived  somewhere  on  the  land 
surfaces  of  Carboniferous  time.     Such  undoubtedly  was  the 
reptilian    protot>i)e    from    which    evolved   every   one    of   the 
marvellous  mechanical  types  which  we  may  now  briefly  re- 
view.    By  methods  first  clearly  enunciated  by  Huxley  in  1880 
several  of  the  ideal  vertebrate  prototypes  have  been  theoreti- 
cally reconstructed,  and  in  more  than  one  instance  discovery 
has  confirmed  these  hypothetical  reconstructions. 

The  early  geologic  vistas  of  this  entire  radiation  are  seen 
in  the  reptilian  life  of  the  Permian  Epoch  of  North  America, 
Europe,  and  Africa  just  described,  consisting  exclusively  of  ter- 
restrial and  terrestrio-aquatic  forms.  In  the  Triassic  we  obtain 
succeeding  vistas  of  the  terrestrial  and  fluviatile  life  of  North. 


ADAPTIVE   RADIATION  OF   REPTILES 


195 


America,  Europe,  and  Africa,  as  well  as  our  first  glimpses  of  the 
early  marine  life  of  North  America.  In  Jurassic  time  deposits 
at  the  bottom  of  the  great  interior  continental  seas  give  us  the 


TERRESTRIAL  AND 
FLUVIATILE 


UPPER 
CRETACEOUS 


FINAL  DINOSAUR  STAGES 
(PREDENTATA  AND  ThEROF^DA) 


LOWER 
CRETACEOUS 

tCOMANCHEAN) 


JURASSIC 


MARIN^ 
N.  AMER.    I  EUROPE    I   AFRICA  .   I   S.  AMER. 


FINAL  REPTILIAN  SEA  FAUNA 
(PLESIOSAURS  AND  MOSASAURS> 


TRIASSIC 


Fig.  73.    Geologic  Records  of  Reptilian  Evolution,  Terrestrial  and 

Marine. 

Shaded  areas  represent  the  geologic  vistas  of  reptilian  life  which  have  been  discovered 
from  fossils  entombed  in  ancient  terrestrial,  fluviatile,  and  marine  habitats  of 
different  portions  of  the  northern  and  southern  hemispheres. 

Triassic.  We  begin  with  the  deposits  of  the  continental  surfaces  of  North  America, 
Europe,  and  Africa.  During  Triassic  time  the  first  dinosaur  stages  appear,  as  well 
as  some  of  the  semi-aquatic  forms  which  frequented  fluviatile  regions,  while  the  primi- 
tive ichthyosaurs  were  then  fully  adapted  to  marine  life. 

Jurassic  and  Lower  Cretaceous.  We  continue  with  geologic  vistas  of  the  succeeding 
marine  life  and  the  evolution  of  the  secont)  reptilian  sea  fauna,  indicated  by  the 
shaded  areas  of  the  Jurassic  and  the  Lower  Cretaceous  of  North  America  and  Europe. 
The  remains  of  these  animals  are  found  in  the  deposits  of  deep  or  shallow  sea  waters. 
There  is  one  great  vista,  the  second  dinosaur  stages,  which  includes  the  terrestrial 
dinosaurs  known  as  Sauropoda,  found  in  Upper  Jurassic  and  Lower  Cretaceous  de- 
ix)sits  in  North  America,  Europe,  Africa,  and  South  America. 

Upper  Cretaceous.  Then  there  was  a  long  interval,  followed  by  the  final  dinosaur 
stages  and  a  long  vista  of  tTie  terrestrial  reptilian  life  of  Upper  Cretaceous  time,  especi- 
ally in  North  America.     Contemporary  with  this  is  the  final  reptilian  sea  fauna. 

Chart  by  the  author. 

second  reptilian  sea  fauna  of  plesiosaurs  and  ichthyosaurs  within 
the  continents  of  North  America  and  Europe.  The  story  of  the 
marine  pelagic  evolution  of  the  reptiles  is  continued  with  some 
interruptions  through  the  Lower  Cretaceous  into  the  final  rep- 


i  It 


196 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


tilian  sea  fauna  of  plesiosaurs  and  mosasaurs  of  Upper  Creta- 
ceous time. 

In  the  meanwhile  the  Ufe  of  the  continents  is  revealed  in 
the  terrestrial  and  fluviatile  deposits  of  the  Triassic  Epoch, 
in  the  first  stages  of  the  terrestrial  evolution  of  the  dinosaurs, 
in  the  early  stages  of  the  fluviatile  evolution  of  the  Crocodilia, 
and  in  the  final  stages  of  the  terrestrial  phases  of  the  Amphibia 
and  pro-Reptilia.  A  long  interval  of  time  elapses  at  this 
period  in  the  earth's  history,  during  which  the  life  of  the  con- 
tinents is  entirely  unknown,  until  the  close  of  the  Jurassic 
and  beginning  of  Cretaceous  time,  when  there  appears  a  sec- 
ond great  stage  of  dinosaur  evolution,  revealed  especially  in 
the  lagoon  deposits  of  North  Africa  and  South  America,  which 
have  yielded  remains  of  giant  Sauropoda.  Then  another  gap 
occurs  in  the  story  as  told  by  continental  deposits.  Finally,  in 
Upper  Cretaceous  time  we  again  discover  great  flood-plain  and 
shore-line  deposits,  which  give  a  prolonged  vista  of  the  ter- 
restrial life  of  the  Reptilia,  especially  in  North  America  and 

Europe. 

Thus  it  will  be  understood  that,  while  the  great  tree  of 
reptiHan  descent  has  been  worked  out  through  a  century  of 
scientific  researches,  beginning  with  those  of  Cuvier  and  con- 
tinued by  Owen,  Leidy,  Cope,  Marsh,  and  our  contemporary 
paleontologists,  there  are  enormous  gaps  in  both  the  terres- 
trial and  the  marine  history  of  several  of  the  reptilian  orders 
which  remain  to  be  filled  by  future  exploration.  We  piece  to- 
gether fossil  history  on  the  continents  and  in  the  seas  from 
the  animals  entombed  in  these  deposits,  partly  by  means 
of  the  real  relationships  observed  in  widely  migrating  forms, 
such  as  the  land  dinosaurs  and  the  marine  ichthyosaurs,  ple- 
siosaurs, and  mosasaurs.  Many  of  these  reptiles  ranged  over 
every  continent  and  in  every  sea.     On  the  whole,  the  physio- 


ADAPTIVE   RADIATION  OF   REPTILES 


197 


graphic  condition  most  favorable  to  the  preservation  of  life 
in  the  fossil  condition  is  that  known  as  the  flood-plain,  in  which 
the  rising  waters  arid  sediments  of  the  rainy  season  rapidly 
entomb   animal  remains  which  are  deposited  on  the  surface 


Fig.  74.    Close  of  the  Age  of  Reptiles.    A  Relic  of  Ancient  Flood-plain  Condi- 
tions. 

Iguanodont  dinosaur  lying  upon  its  back.  Integument  impressions  preserved.  The 
"dinosaur  mummy,"  Trachodon,  from  the  Upper  Cretaceous  flood-plain  deposits  of 
Converse  County,  Wyoming.  Due  to  arid  seasonal  desiccation,  the  skin  folds  and 
impressions  are  preserved  over  the  greater  part  of  the  body  and  limbs.  Discovered 
by  Sternberg.     JMounted  specimen  in  the  American  Museum  of  Natural  History. 

or  in  small  water  pools  during  the  drier  seasons.  Fossils 
buried  in  old  flood-plain  areas  of  South  Africa  tell  us  the  story 
of  the  life  evolution  which  is  continued  by  the  ancient  shore 
and  lagoon  deposits  in  other  parts  of  the  world  as  well  as  by 
fossils  found  in  the  broad,  intermittent  flood-plain  areas  of 
the  American  Triassic  and  Cretaceous,  which  close  with  the 


1 98  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

great  delta  deposits   of   the  Upper  Cretaceous  lying  to  the 
east  of  the  present  Rocky  Mountain  range.     The  more  re- 
stricted deposition  areas  of  drying  pools  and  lagoons,  such  as 
those  observed  in  the  Permian  and  Triassic  shales  and  sand- 
stones of  Texas,  entomb  many  forms  of  terrestrial  life.     Vistas 
of  the  contemporaneous  evolution  of  fluviatile,  aquatic,  and 
marine  life  are  afiforded  by  the  animals  which  perish  at  the 
surface  and  sink  to  the  calcareous  bottom  oozes  of  the  conti- 
nental seas  of  Triassic,  Jurassic,  and  Cretaceous  time.     It  is 
only  in  the  Tertiary  of  the  Rocky  Mountain  region  of  North 
America  that  we  obtain  a  nearly  continuous  and  uninterrupted 
story  of  the  successive  forms  of  continental  life,  among  the 
mammals  entombed  in  the  ancient  flood-plains,  in  the  volcanic 
ash-beds,  in  the  lagoons,  and  more  rarely  in  the  littoral  deposits. 

Aquatic  Adaptation  of  the  Reptilia,  Direct  and 

Reversed 

From  the  distinctively  terrestrial  radiations  of  Permian 
time  we  turn  to  the  development  of  aquatic  habitat  phases 
among  the  reptiles  which  lived  along  the  borders  of  the  great 
interior  rivers  and  continental  seas  of  Permian,  Triassic,  and 

Jurassic  time. 

This  reversal  of  adaptation  from  terrestrial  into  aquatic 
life  is,  as  we  might  theoretically  anticipate,  a  reversal  of  func- 
tion rather  than  of  structure,  because,  as  above  stated  (p.  159), 
it  is  a  universal  law  of  form  evolution  that  ancient  adaptive 
characters  once  lost  by  the  heredity-chromatin  are  never 
reacquired.  In  geologic  race  evolution  there  is  no  process 
analogous  to  the  wonderful  phenomena  of  individual  regenera- 
tion or  regrowth,  such  as  is  seen  among  amphibians  and  other 
primitive  vertebrates,  whereby  the  original  limb  may  be  com- 
pletely restored  from  the  mutilated  remnant  of  an  amputation. 


\ 


i 


AQUATIC  REPTILES 


199 


REPnuA 


CHAMPSOSAURUS 


UPPER 
CRETACEOUS 


Such  regeneration  is  attributable  to  the  potentiality  of   the 
heredity-chromatin  which  still  resides  in  the  cells  of  the  am- 
putated surfaces.     The  heredity-chromatin  determiners  of  the 
bones  of  the  separate  digits  or  separate  phalanges  if  once  lost 
in  geologic  time  are  never  reacquired;    on  the  contrary,  each 
phase   of  habitat   adapta- 
tion is  forced  to  commence 
with  the  elements  remain- 
ing in  the  organism's  hered- 
ity-chromatin, which  may 
have  been  impoverished  in 
previous   habitats.     When 
an  ancient  habitat  zone  is 
reentered    there    must    be 
rcadaptation   of    the   parts 
which  remain.     Thus, 
when    the    terrestrial   rep- 
tiles   reenter    the    aquatic 
zone    of    their    amphibian 
ancestors  they  cannot  re- 
sume the  amphibian  char- 
acters, for  these  have  been 
lost  by  the  chromatin. 
This  invariable  princi- 


REPTIUA 


RHYTIDODON 


TRIASSIC 


Fig.  75.  Reptiles  Leaving  a  Terrestrial 
FOR  AN  Aquatic  Habitat,  the  Beginning 
OF  Aquatic  Adaptation. 

Littoral-fluviatile  types  independently  evolve 
in  the  Triassic  {Rhytidodon,  a  phytosaur)  and 
in  the  Upper  Cretaceous  {Champsosaurus). 
These  animals  belong  to  two  widely  different 
orders  of  reptiles,  neither  of  which  is  closely 
akin  to  the  modern  alligators  and  crocodiles. 
The  adaptation  is  convergent  to  that  of  the 
existing  gavials  and  crocodiles.  Restorations 
for  the  author  by  W.  K.  Gregory  and  Richard 
Deckert. 


pie  underlying  reversed 
evolution  is  partly  illustrated  (Fig.  53)  ^  the  passage  from  the 
reptilian  foot  into  the  fin  of  the  aquatic  reptile  and  with  equal 
clearness  in  the  passage  of  the  wing  of  the  flying  bird  into  the 
fin  of  the  swimming  bird  (Fig.  no). 

In  no  less  than  eleven  out  of  the  eighteen  orders  of  reptiles 
reversed  adaptation  to  a  renewal  of  aquatic  life,  like  that  of 
the  fishes  and  amphibians,  took  place  in  the  long   and  slow 


200 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


REPnUA 


CYM8OSPON0YLUS 


TRIASSIC 


REPT1UA 


GEOSAURUS 


JURASSIC 


REPnuA 


TYLOSAURUS 


CRETACEOUS 


CRICOTUS 


AMPHIBIA 


PCRMO- 
CARBONIFEROUS 


Fig.  76.  Convergent  Aquatic  Adap- 
tation INTO  Elongate  Fusiform  Type 
IN  Four  Different  Orders  of 
Amphibians  and  Reptiles. 

Independently  convergent  evolution  of  four  long- 
bodied,  free-swimming,  swift-moving,  surface-liv- 
ing aquatic  types  in  which  the  fins  and  limbs  are 
retained  as  paddles:  Crico/M5,  an  amphibian;  Ty- 
losaurus,  an  Upper  Cretaceous  mosasaur;  Geo- 
saurus,  a  Jurassic  crocodilian;  Cymbospondylus,  a 
Triassic  ichthyosaur.  A  very  similar  fusiform  type 
evolves  among  the  mammals  in  the  Eocene  ceta- 
ceans {Zeuglodon),  as  seen  in  Fig.  123.  Restora- 
tions prepared  for  the  author,  independent  of 
scale,  by  W.  K.  Gregory  and  Richard  Deckert. 


passage  from  a  terrestrial  phase, 
through  palustral,  swamp-living 
phases  into  a  Httoral,  fluviatile 
phase,  and  from  this  into  Httoral 
and  marine  salt-water  phases; 
so  that  finally  in  no  less  than 
six  orders  of  reptiles  the  pelagic 
phase  of  the  high  seas  was  inde- 
pendently reached. 

The  role  in  the  economy  of 
oceanic  life  w^hich  is  now  taken 
by  the  whales,  dolphins,  and  por- 
poises was  assumed  by  families 
of  the  plesiosaurs,  ichthyosaurs, 
mosasaurs,   snakes,   and   croco- 
diles, all  flourishing  in  the  high 
seas,  together  with  families  of 
the  turtles,  which  are  the  only 
high-sea  reptiles  surviving  at  the 
present  day.     Moreover,  under 
the  alternating  adaptations  to 
terrestrial  and  marine  life,  which 
prevailed  during  the  10,000,000 
years    of    late    Palaeozoic    and 
Mesozoic  time,  several  families 
of  the  existing  orders  of  reptiles 
sought  a  seafaring    existence 
more  than  once  and  gave  off 
numerous   side   branches    from 
the   main   stem.     The   adapta- 
tions to  marine  Hfe  have  been 
especially   studied  by   Fraas. 


AQUATIC  REPTILES 


201 


Even  to-day  there  are  tendencies  toward  marine  invasion 
observed  among  several  of  the  surviving  families  of  lizards 
and  crocodiles  of  seashore  frequenting  habits. 


ADAPTIVE  RADIATION  OF  AQUATIC  REPTILES 


TERRESTRIAL 
(LAND  UVING) 


PALUDAL 
(SWAMP  LIVING) 


LinORAL- 

FLUVIATILE 
(FRESH  WATER) 


LinORAL- 

MARINE 

(SALT  WATER) 


PELAGIC 


Fig.  77.    Independent  Reversed  Adaptation  to  the  Aquatic  Zones  in  Twelve 
Orders  of  Reptiles,  Originating  on  Land  and  Entering  the  Seas. 

Diagram  showing  the  manner  in  which  twelve  of  the  eighteen  orders  of  reptiles  descend 
from  the  terrestrial  (land-living)  zone  into  the  paludal  (swamp-frequentmg)  zone  thence 
into  the  littoral-fluviatile  (fresh-water  and  brackish-water)  zone,  thence  mto  the  httoral- 
marine  (salt-water)  zone,  and  fmally  into  the  pelagic  zones  of  the  high  seas.  This  final 
marine  pelagic  phase  of  evolution  is  attained  in  only  six  orders,  namely,  the  plesiosaurs 
Chelonia  (sea-tortoises),  ichthyosaurs,  mosasaurs  (marine  lizards)  crocodiles  and 
certain  ophidians  (true  sea-snakes  found  far  out  at  sea  in  the  Indian  Ocean).  Nine  of 
the  reptilian  orders  give  off  not  only  one  but  from  two  to  five  independent  branches 
seeking  aquatic  life,  of  which  sLx  independently  reach  the  full  pelagic  high-sea  phase. 

Still  more  remarkable  than  the  law  of  reversed  adaptation 
is   that   of   alternate   adaptation,   which   has  been  brilliantly 


t  i 
j 


202 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


developed  by  Louis  Dollo,  of  Brussels.     This  is  applied  hypo- 
thetically  to  the  evolution  of  the  existing  leatherbacks  (Sphar- 


1       ANCESTRAL  CHELONIANS 


TERR2  AQUATIC  -.  ^'^"  ^'-*°  carapace 

I  kllll      #-I^V/l-l  i  t\>    ^       ^^p  PLASTRON 


AQUATIC,FLUVt5,^ — 


"^  PRIMARY  LITTORAL  STAGE 


..  I    ITTADAI  ^W  WITH  UNIMPAIRED  CARAPACE 

"  Li  li  URAL       I  AND  PLASTRON 


PELAGIC 
ABYSSAL 


AND  PLASTRON 

PRIMARY  PELAGIC  STAGE 

WITH  CARAPACE  AND  PLASTRON 

PROGRESSIVELY  ATROPHIED 


a\  secondary  littoral  stage 
'  primary  carapace  and  plastron  reduced 
a  secondary  carapace  and  plj^f.tacln  <^f  dermal  ossicles  i 

/g  secondary  pelagic  stage 
>ap|  secondary  carapace  regressive 
Secondary  plastron  reduced       _ 


Fig.  78.    Chelonia.     Diagram  Illustrating   the  Alternate  Habitat  Migration 

OF  THE  Ancestral  "Leatherbacks,"  Sphargida. 

DoUo's  theory  is  that  these  animals  originate  in  armored  land  forms  with  a  soHd  bony- 
shell,  and  pass  from  the  terrestrio-aquatic  into  the  littoral  and  then  into  the  pelagic 
zone,  in  which  the  solid  bony  shell,  being  no  longer  of  use,  is  gradually  atrophicxl.  After 
prolonged  marine  pelagic  existence  these  animals  return  secondarily  to  the  littoral 
zone  and  acquire  a  new  armature  of  rounded  dermal  ossicles  which  develop  on  the 
upper  and  lower  shields  of  the  body.  The  animals  (Sphargis)  then  for  a  second  time 
take  up  existence  in  the  pelagic  zone,  during  which  the  dermal  ossicles  again  tend  to 
disappear. 

gidae),  an  extremely  specialized  type  of  sea  turtles.     It  is  be- 
lieved that  after  a  long  period  of  primary  terrestrial  evolution 

in  which  the  ancestors  of 
these  turtles  acquired  a  firm, 
bony  carapace  for  land  de- 
fense, they  then  passed 
through  various  transitions 
into  a  primary  marine  phase 
during  which  they  gradually 
lost  all  their  first  bony  arma- 
ture. Following  this  sea 
phase  the  animals  returned 
to  shore  and  entered  a 
secondary  littoral,  shore-liv- 
ing phase,  also  of  long  dur- 
ation, in  course  of  which  they  developed  a  second  bony 
armature  quite  distinct  in  plan   and  pattern   from   the  first. 


Fig.    79.    The    Existing     "Leatherback" 
Chelonian  Sphargis. 

In  this  form  the  solid  armature  adapted  to  a 
former  terrestrial  existence  is  being  replaced 
by  a  leathery  shield  in  which  are  embedded 
small  polygonal  ossicles.     After  Lydekker. 


AQUATIC   REPTILES 


203 


Descendants  of  these  secondarily  armored,  shore-living  types 
again  sought  the  sea  and  entered  a  secondary  marine  pelagic 
phase  in  course  of  which  they  lost  the  greater  part  of  their 


ARCHELON 


REPTILIA 


CRETAcloUS    REPTILIA 


PLACOCHELYS 


TRIASSIC 


Fig.  80.    Armored  Terrestrl\l  Chelonia 

Invade  the  Seas  and  Lose  Their  Arma- 
ture. 
Convergent    or    analogous    evolution     (two 

upper  figures)  in  the  inland  seas  of  the 

paddle-propelled  chelonian  Archelon  (after 

Williston),  the  gigantic   marine  turtle  of 

the  Upper  Cretaceous  continental  seas  of 

North  America,  and  of  Placochelys  (after 

Jaekel  in  part),  a  Triassic  reptile  belonging 

to  the  entirely  distinct  order  Placodontia. 
Skeleton  of  Archelon   (lower)  in   which  the 

bony  armature  of  the  carapace  has  largely 

disappeared,  exposing  the  ribs.     Specimen 

in  the  Peabody  Museum  of  Yale  Univer- 
sity.   After  Wieland. 

second  armature  and  acquired  their  present  leathery  covering, 
to  which  the  popular  name  'leatherbacks''  appHes.^ 

In  general  the  law  of  reversed  aquatic  adaptation  is  most 
brilliantly  illustrated  in  the  fossil  ichthyosaurs,  in  the  internal 

1  This  law  of  alternate  adaptation  may  be  regarded  as  absolutely  established  in  the 
case  of  certain  land-living  marsupials  in  which  anatomical  records  remain  of  an  alterna- 
tion of  adaptations  from  the  terrestrial  to  the  arboreal  phase,  from  an  arboreal  into  a 
secondary  terrestrial  phase,  and  from  this  terrestrial  repetition  to  a  secondary  arboreal 
phase  The  relics  of  successive  adaptations  to  alternations  of  habitat  zones  and  adap- 
tive phases  are  clearly  observed  in  the  so-called  tree  kangaroos  {Dendrolagus)  of  Australia. 


204 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


anatomy  of  which  land-living  ancestry  is  clearly  written,  while 
reversed  adaptation  for  marine  pelagic  life  has  resulted  in  a 
superficial  type  of  body  which  presents  close  analogies  to  that 
of  the  sharks,  porpoises,  and  shark-dolphins  (Fig.  41).  Integu- 
mentary median  and  tail  fins  precisely  similar  to  those  of  the 


Fig.  81.    Extreme  Adaptation  of  the  Ichthyosaurs  to  Marine  Pelagic  Life. 

Although  primarily  of  terrestrial  origin  the  ichthyosaurs  become  quite  independent  of 
the  shores  through  the  viviparous  birth  of  the  young  as  evidenced  by  a  fossil  female 
ichthyosaur  (upper  figures)  with  the  foetal  skeletons  of  seven  young  ichthyosaurs 
within  or  near  the  abdominal  cavity. 

A  fossil  ichthyosaur  (lower  figure)  with  preserved  body  integument  and  fin  outlines  re- 
sembling those  of  the  sharks  and  dolphins  (see  Fig.  41). 

Both  specimens  in  the  American  Museum  of  Natural  History  from  Holzmaden,  Wurtem- 

berg. 

sharks  evolve,  the  anterior  lateral  limbs  are  secondarily  con- 
verted into  fin-paddles,  which  are  externally  similar  to  those 
of  sharks  and  dolphins,  while  the  posterior  limbs  are  reduced. 
As  in  the  shark,  the  tail  fin  is  vertical,  while  in  the  dolphin  the 
tail  fin  is  horizontal.  In  the  early  history  of  their  marine 
pelagic  existence  the  ichthyosaurs  undoubtedly  returned  to 
shore  to  deposit  their  eggs,  but  a  climax  of  imitation  of  the  dol- 
phins and  of  certain  of  the  sharks  is  reached  in  the  develop- 
ment of  the  power  of  viviparity,  the  growth  of  the  young  within 


AQUATIC  REPTILES 


205 


REPTILIA 


BAPTANODON 


CRETACEOMS 


REPTIUA 

Fig.  82. 


CYMBOSPONDYLUS 


TRIASSIC 


the  body  cavity  of  the  mother,  resulting  in  the  young  ichthyo- 
saurs being  born  in  the  water  fully  formed  and  able  to  take 
care  of  themselves  immediately  after  birth  like  the  young  of 
modern   whales   and   dolphins.     When   this   viviparous   habit 
finally  released  the  ichthyosaurs  from  the  necessity  of  return- 
ing  to   land   for  breeding   they   developed   the   extraordinary 
powers  of  migration  which  car- 
ried them  into  the  Arctic  seas 
of  Spitzbergen,  the  Cordilleran 
seas  of  western  North  America, 
and  doubtless  into  the  Antarc- 
tic.    So  far   as  we   know   this 
viviparous  habit  was  never  de- 
veloped   among    the    seafaring 
turtles,    which    always    return 
to  shore  to  deposit  their  eggs. 
While    the    ichthyosaurs    vary 
greatly  in  size,  they  present  a 
reversed  evolution  from  the  ter- 
restrial, quadrupedal  type  into 
the  swift-moving,  fusiform  body 
type  of  the  fishes,   which  is 
finally   reduced    in   predaceous 
power  through  the  degeneration  of  the  teeth,  as  observed  in 
the  Baptanodon,  an  ichthyosaur  of  the  Upper  Jurassic  seas  of 
the  ancient  Rocky  Mountain  region. 

While  the  continental  seas  of  Jurassic  time  were  favorable 
to  this  remarkable  aquatic  marine  phase  of  the  reptiles,  still 
greater  inundations  both  of  North  America  and  of  Europe 
occurred  during  Upper  Cretaceous  time.  This  was  the  period 
of  the  maximum  evolution  of  the  sea  reptiles,  the  ultimate 
food  supply  of  which  was  the  surface  life  of  the  oceans,  the 


Restorations  of  Two  Ich- 
thyosaurs. 

Cymhospondyhis,  a  primitive  ichthyosaur 
from  the  Triassic  seas  of  Nevada  (after 
Merriam),  and  the  highly  specialized 
Baptanodon,  a  Cretaceous  ichthyosaur 
of  the  seas  of  that  period  in  the  region 
of  Wyoming,  in  which  the  teeth  are 
greatly  reduced.  Restorations  for  the 
author  by  W.  K.  Gregory  and  Richard 
Deckert. 


2o6  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

marine  Protozoa,  skeletons  of  which  were  depositing  the  great 
chalk  beds  of  Europe  and  of  western  North  America. 

The  Plesiosaurs  had  begun  their  invasion  of  the  sea  during 
Upper   Triassic   time,   as   shown    in    the  primitive  half-lizard 


Fig.  83.  North  America  in  Upper  Cretaceous  Time. 
The  great  inland  continental  sea  extending  from  the  Gulf  to  the  Arctic  Ocean,  was  favor- 
able to  the  evolution  of  the  mosasaurs,  plesiosaurs,  and  giant  sea  turtles  {Archelon). 
This  period  is  marked  by  the  greatest  inundation  of  North  America  during  Mesozoic 
time,  by  mountains  slowly  rising  along  the  Pacific  coast  from  Mexico  to  Alaska,  and  by 
volcanic  activity  in  Antillia.  Detail  from  the  globe  model  in  the  American  Museum  by 
Chester  A.  Reeds  and  George  Robertson,  after  Schuchert. 

Lariosaurus,  discovered  in  northern  Italy,  which  still  retains 
its  original  lacertilian  appearance,  due  to  the  fact  that  the 
Hmbs  and  feet  are  not  as  yet  transformed  into  paddles.  In 
the  subsequent  evolution  of  paddles  the  number  of  digits  re- 
mains the  same,  namely,  five,  but  the  number  of  the  phalanges 
on  each  digit  is  greatly  increased  through  the  process  known 
as  hyperphalangy,  an  example  of  the  numerical  addition  of 


AQUATIC   REPTILES 


207 


new  characters.     Propulsion  through  the  water  was  rather  by 
means  of  the  paddles  than  by  the  combined  lateral  body-and- 


FiG.  84.    Convergent  Forms  of  Aquatic  Reptiles  of  Different  Origin. 

Lariosaurus  (left),  the  Triassic  ancestor  of  the  plesiosaurs  from  northern  Italy,  and 
Mesosaurus  (right),  from  the  Permian  of  Brazil  and  South  Africa,  representing  another 
extinct  order  of  the  Reptilia,  the  Proganosauria.     Drawn  by  Deckert  after  McGregor. 

tail  motion  seen  among  the  ichthyosaurs,  because  all  plesiosaurs 
exhibit  a  more  or  less  abbreviated  tail  and  a  more  or  less 
broadly  depressed  body.     It  is  also  significant  that  the  fore 


Fig.  85.    A  Plesiosaur  from  the  Jurassic  of  England. 

Skeleton  of  Cryptodeidus  oxonicnsis  seen  from  above.     Mounted  in  the  American  Museum 

of  Natural  History. 


208 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


^^/    ■=^n 


and  hind  paddles  are  homodynamic,  I  e.,  exerting  equal  power; 
they  are  so  exactly  alike  that  it  is  very  difficult  to  distinguish 
them,  whether  they  are  provided  with  four  broad  paddles  or 
with    four    long,    narrow,    slender    paddles.     The    plesiosaurs 

afford   the  first  illustration  we 
have  noted  of  another   of   the 
great   laws  of   form  evolution, 
namely,  adaptation  occurs  far 
more     frequently     through 
changes  of  existing  proportions 
than  through   numerical   addi- 
tion of  new   characters.     It   is 
proportional    changes    which 
separate    the    swift-moving 
plesiosaurs  {Trinacromerion  os- 
borni),    which    are    invariably 
provided  with  long  heads,  short 
necks,  and  broad  paddles,  from 
the    slow-moving   plesiosaurs 
(Elasmosaurus) ,  which  are  pro- 
vided with  narrow  paddles, 
short    bodies,    extremely    long 
necks,  and  small  heads. 

It  is  believed  that  the  lizard- 
like ancestors  of  the  mosasaurs 
left  the  land  early  in  Cretaceous 
time;  it  is  certain  that  through- 
out the  three  or  four  million  years  of  the  Cretaceous  epoch 
they  spread  into  all  the  oceans  of  the  world,  from  the  conti- 
nental seas  of  northern  Europe  and  North  America  to  those 
of  New  Zealand.       In  Europe  these  animals  survived  to  the 
very  close  of  Mesozoic  time  since  the  type  genus  of  the  great 


TRtNACROMCmON 


CnETACCOUS 


Fig.  86.  Types  of  Marine  Pelagic 
Plesiosaurs  of  the  American  Con- 
tinental Cretaceous  Seas. 

The  slow-moving,  long-necked  Elasmo- 
saiirus  and  the  swift-moving,  short- 
necked  Trinacromerion.  The  limbs 
are  completely  transformed  into  pad- 
dles. The  great  differences  in  the  pro- 
portions of  the  neck  and  body  repre- 
sent adaptations  to  greater  or  less 
speed.  Restorations  for  the  author  by 
W.  K.  Gregory  and  Richard  Deckert, 
chiefly  after  Williston. 


AQUATIC  REPTILES 


209 


order    Mosasauria    (Mosasaurus)^   taking  its  name  from  the 

River  Meuse,  was  found  in  the  uppermost  marine  Cretaceous. 

Detailed  knowledge  of  the  structure  of  these  remarkable 

sea  lizards  is  due  chiefly  to  the  researches  of  Williston  and 


Fig.  87.    A  Sea  Lizard. 

Tylosaurus,  a  giant  mosasaur  from  the  inland  Cretaceous  seas  of  Kansas,  chasing  the  giant 
fish  Portheus.  After  a  restoration  in  the  American  Museum  of  Natural  History,  by 
Charles  R.  Knight  under  the  author's  direction. 

Osborn  of  this  country  and  to  those  of  Dollo  in  Europe.  The 
head  is  long  and  provided  with  recurved  teeth  adapted  to  seiz- 
ing active  fish  prey  (Fig.  87);  the  neck  is  extremely  short;  as 
in  the  plesiosaurs  the  fore  and  hind  Umbs  are  converted  into 
paddles,  symmetrical  in  proportion;  the  body  is  elongate  and 


2IO 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


propulsion  is  not  chiefly  by  means  of  the  fins  but  by  the  sinu- 
ous motions  of  the  body,  and  especially  of  the  very  elongate, 
broad,  fin-like  tail.  These  sea  lizards  of  Upper  Cretaceous 
time  (Fig.  76)  are  analogous  or  convergent  to  the  sea  Croco- 
dilia  (Geosaums)  of  Jurassic  time  and  present  further  analogies 
with  the  Triassic  ichthyosaur  Cymbospotidylus  and  the  small 
Permo-Carboniferous  amphibian  Cricotiis  (Fig.  76).  In  the 
American  continental  seas  these  animals  radiated  into  the 
small,  relatively  slender  Clidastes,  into  the  somewhat  more 
broadly  finned  Platecarpus,  and  into  the  giant  Tylosaurus, 
which  was  capable  (Fig.  87)  of  capturing  the  great  fish  of  the 
Cretaceous  seas  {Portheus). 

Terrestrial  Life.     Carnivorous  Dinosaurs 

Widely    contrasting    with    these    extreme    adaptations    to 
aquatic  marine  life,  the  climax  of  terrestrial  adaptation  in  the 
reptilian  skeleton  is  reached  among  the  dinosaurs,  a  branch 
which  separated  in  late  Permian  or  early  Triassic  time  from 
small   quadrupedal,    swiftly    moving,    lizard-like    reptiles   and 
before  the  time  of  their  extinction  at  the  close  of  the  Creta- 
ceous had  evolved  into  a  marvellous  abundance  and  variety 
of  types.     In  the  Upper  Triassic  of  North  America,  late  New- 
ark time,  the  main  separation  of  the  dinosaurs  into  two  great 
divisions,    (a)    those   with   a   crocodile-like   pelvis,   known   as 
Saurischia,  and  {b)  those  with  a  bird-like  pelvis,  known  as  Orni- 
thischia,  had   already   taken  place,  and  the  dinosaurs  domi- 
nated all  other  terrestrial  forms. 

When  Hitchcock  in  1836  explored  the  giant  footprints  in 
the  ancient  mud  flats  of  the  Connecticut  valley  he  quite  nat- 
urally attributed  many  of  them  to  gigantic  birds,  since  at  the 
time  the  law  of  parallel  mechanical  evolution  between  birds 
and   dinosaurs  was  not   comprehended   and   the  order  Dino- 


CARNIVOROUS  DINOSAURS 


211 


STEGOMUS 


ANOMOEPUS 


PODOKESAURUS 


ANCHISAURUS 


RHYTIDODON 


CONNECTICUT 


TRJASSIC 


REPTILES 


Fig.  88.    Life  of  the  Connecticut  River  Valley  in  Upper  Triassic  (Newark)  Time. 

Anchisaurus,  a  primitive  carnivorous  bipedal  dinosaur.  Rhytidodon,  a  phytosaur  analo- 
gous but  not  related  to  the  modern  gavials.  Stegomus,  a  small  armored  phytosaur 
related  to  Rhytidodon.  Anonurpus,  a  herbivorous  bipedal  dinosaur  related  to  the 
"duckbills"  or  Iguanodonts.  Podokesaurus,  a  light,  swift-moving,  carnivorous  dino- 
saur of  the  bird-like  type.  Restorations  (except  Rhytidodon)  after  R.  S.  Lull  of  Yale 
University.     Drawn  to  uniform  scale  for  the  author  by  Richard  Deckert. 


cmWcStoo* 


tCOMAMCMt*" 


PMYLOGENY  AND  ADAPTIVE  RADIATION  OF  THE  DINC^URS 


LAST  SAUKOKXM 


LAST  CAKNIVOMOUS  DINOSAUMS 


B 


LAST  »RO-UKE   DINOSAURS 


LAST  BEAKED  DINOSAURS 
(OUCK-BIU-S.  CTCJ 


LAST  ARMORED  DINOSAURS 


D 


.  VAWO  *AURO*QOA  - 


VARICO  eAKNrVOROUS  DINOSAUR*  ' 


MRDUKC  DINOSAURS - 


-BEAKED  DINOSAURS  ' 


ARMORED  DINOSAURS  - 


JUHAaWC 


mvMrnvt  SAuRorooA 


FCNNSVLVAMAN 


ANCCST1«AL  SAUnOKOA  MMimvt  CARNIVOROUS  DINOSAURS 

FIRST  BIRD-LIKE  OMOSAun* 


V. 


/ 


FIRST  ARMORED  DINOSAURS 


FIRST  HORNY^EAKED  DINOSAURS 
•aiPCDAU 


Z^ 


FIRST  CARNIVOROUS  DINOSAURS 


COMMON  STOCK  OF  DINOSAURS,  CROCODILES. 
aiROS  PTEROSAURS  ETC 


FIRST  REinx.CS 


Fig.  89.  Terrestrial  Evolution  of  the  Dinosaurs. 
The  ancestral  tree  of  the  dinosaurs,  originating  in  Lower  Permian  time,  and  branching 
into  five  great  lines  during  a  period  estimated  at  twelve  million  years.  A,  The  giant 
herbivorous  Sauropoda  which  sprang  from  Lower  Triassic  carnivorous  ancestors. 
B,  Giant  carnivorous  dinosaurs,  which  prey  upon  all  the  larger  herbivorous  forms. 
C  Swift-moving,  ostrich-like,  carnivorous  dinosaurs,  related  to  B.  D,  Herbivorous 
Iguanodonts,  swift-moving,  beaked,  or  "duck-bill"  dinosaurs,  related  to  E.  ^^  Slo.v- 
moving,  quadrupedal,  heavily  armored  or  homed  herbivorous  dmosaurs,  related  to  D. 
Prepared  for  the  author  by  W.  K.  Gregory,  chiefly  after  Lull. 


t 


212 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


sauria  was  not  known.  It  has  since  been  discovered  that 
many  of  the  ancient  dinosaurs,  especially  those  of  carnivorous 
habit,  were  bird-footed  and  adapted  in  structure  for  rapid, 
cursorial  locomotion;  the  body  was  completely  raised  above 


Fig.  90.  North  America  in  Upper  Triassic  (Newark)  Time. 
The  period  of  the  primitive  bipedal  dinosaurs,  with  semi-arid,  cool  to  warm  climate  and 
a  prevailing  flora  of  cycads  and  conifers.  Remains  of  amphibians,  primitive  crocodiles, 
and  dinosaurs  are  found  in  the  reddish  continental  deposits.  Detail  from  the  globe 
model  in  the  American  Museum  by  Chester  A.  Reeds  and  George  Robertson,  after 
Schuchert. 

the  ground,  the  forward  part  being  balanced  with  the  aid  of 
the  long  tail.  This  primitive  type  of  body  structure  is  com- 
mon to  all  the  dinosaurs,  and  is  evidence  that  the  group 
underwent  a  long  period  of  evolution  under  semi-arid  conti- 
nental conditions  in  late  Permian  and  early  Triassic  time. 
The  reptilian  group  discovered  in  the  Connecticut  valley  (Fig. 


o 


'I 


CARNIVOROUS  DINOSAURS 


213 


88)  is  not  inconsistent  with  the  theory  of  a  semi-arid  climate 
advocated  by  Barrell  to  explain  the  reddish  continental  de- 
posits not  only  in  the  region  of  the  Connecticut  valley  but 
over  the  southwestern  Great  Plains.  The  flora  of  ferns,  cycads, 
and  conifers  indicates  moderate  conditions  of  temperature. 
Along  the  Pacific  coast  there  was  a  great  overflow  of  the  seas 
along  the  western  continental  border  and  an  archipelago  of 
volcanic  islands.  In  this  region  there  were  numerous  coral 
reefs  and  an  abundance  of   cephalopod  ammonites.     In   the 


r 


/>f 


'^.      -.il'V'-'*- 


^S^*%ii.*.^-^ 


*tmi 


Fig.  91.    A  Carnivorous  Dinosaur  Preying  upon  a  Sauropod. 
Skeletons  (left)  and  restoration  (right)  of  the  bipedal  dinosaur  Allosaurus  of  Upper  Jurassic 
and  Lower  Cretaceous  time  in  the  act  of  feeding  upon  the  carcass  of  Apatosaurus,  one 
of  the  giant  herbivorous  Sauropoda  of  the  same  period.     Mounted  specimens  and 
restoration  by  Osbom  and  Knight  in  the  American  Museum  of  Natural  History. 

interior  continental  seas  great  marine  reptiles  (Cymbospondylus, 
Fig.  82),  related  to  the  ichthyosaurs,  were  abundant. 

The  primitive  light-bodied,  long-tailed  type  of  dinosaur  of 
bipedal  locomotion  originates  in  this  country  with  Marsh's 
Anchisaurus  of  the  Connecticut  valley  (Fig.  88)  and  develops 
into  the  more  powerful  form  of  the  Allosaurus  of  Marsh  from 
the  Jurassic  flood-plains  east  of  the  Rocky  Mountains  (Fig.  91). 
Contemporaneous  with  this  powerful  animal  is  the  much  more 
delicate  Ornitholestes,  which  is  departing  from  the  carnivorous 
habits  of  its  ancestors  and  seeking  some  new  form  of  food.  It 
is  in  turn  ancestral  to  the  remarkable  ''ostrich  dinosaur''  of 
the  Upper  Cretaceous,  Struthiomimus  (Ornithomimus) ,  which 
is  bird-like  both  in  the  structure  of  its  limbs  and  feet  and  in 


•> 


I 


Recently  restored  skeleton  of  the  light-limbed, 
bird-fike,  toothless  "ostrich"  dinosaur,  StriUh- 
iomimus   {Ornithomimus) ,  after  Osbom. 


214  THE  ORIGIN   AND   EVOLUTION  OF  LIFE 

its  toothless  jaw  sheathed  in  horn.     In  this  animal  the  car- 
nivorous  habit  is  completely  lost;  it  is  secondarily  herbivorous. 

Its  limbs  are  adapted  to 
very  rapid  motion. 

In  the  meantime  the 
true  carnivorous  dinosaur 
line    was    evolving    over 
the  entire  northern  hemis- 
phere stage  by  stage  with 
the  evolution  of  the  varied 
herbivorous  group  of  the 
dinosaurs.    These  animals 
preserved  perfect   me- 
chanical unity  in  the  evo- 
lution of   the  very  swift 
motions  of  the  hind  limb 
and   prehensile    powers 
both  of  the  jaws  and  of 
the  hind  feet,  adapted  to 
seizing  and  rapidly  over- 
coming    a     struggling 
powerful  prey.  This  series 
reaches   an    astounding 
climax    in    the    gigantic 
Tyrannosanrus     rex,    de- 
scribed  by  Osbom   from 
the  Upper  Cretaceous  of 
Montana     (see    frontis- 
piece).    This  ^^king  of  the  tyrant  saurians"  is  in  respect  to 
speed,   size,    power,    and    ferocity    the    most    destructive   life 
engine  which  has  ever  evolved.     The  excessively  small  size  of 
the  brain,  probably  weighing  less  than  a  pound,  which  is  less 


CARNIVOROUS  DINOSAURS 


215 


^ 


i^ 


''"vtt^lUUlLijittafc 


Lateral  view  of  the  "tyrant"  dinosaur,  Tyran- 
nosanrus (left),  and  the  "ostrich"  dinosaur, 
Slruthiomimus  (right),  to  the  same  scale. 

Fig.  92.  Extremes  of  Adaptation  in  the 
"Tyrant"  and  the  "Ostrich"  Dinosaurs. 

Skeletons  mounted  in  the  American  Museum  of 
Natural  History. 


\ 


than  I  /4000  of  the  estimated  body  weight,  indicates  that  in 
animals  mechanical  evolution  is  quite  independent  of  the 
evolution  of  their  intelligence;  in  fact,  intelligence  compensates 
for  the  absence  of  mechanical   perfection.     Tyrannosaums  is 


Fig.  93.    Four  Restorations  of  the  "Ostrich"  Dinosaur,  Slruthiomimus 

{Ornilhomimus) . 

A.  Showing  the  mode  of  progression. 

B.  Illustrating  the  hypothesis  that  the  animal  was  an  anteater  which  used  the  front 

claws  like  those  of  sloths  in  tearing  down  anthills. 
C    niustrating  the  hypothesis  that  it  was  a  browser  which  supported  the  fore  part  of  the 
'       body  by  means  of  the  long,  curved  claws  of  the  fore  limb  while  browsmg  on  trees. 
D.  Illustrating  the  hypothesis  that  it  was  a  wading  type,  feeding  upon  shrimps  and 

smaller  crustaceans. 
Restorations  by  Osbom.    No  satisfactory  theory  of  the  habits  of  this  animal  has  as 
yet  been  advanced. 

an  illustration  of  the  law  of  compensation,  first  enunciated  by 
Geoffroy  St.  Hilaire,  first,  in  the  disproportion  between  the 
diminutive  fore  limb  and  the  gigantic  hind  limb,  and  second, 
in  the  fact  that  the  feeble  grasping  power  and  consequent 
degeneration  of  the  fore  limb  and  hand  are  more  than  com- 
pensated for  by  the  development  of  the  tail  and  the  hind  claws, 


1 


i 


111 


REPtlUA. 


PLATEOSAURUS 


TRIASSIC 


2i6  THE  ORIGIN  AND   EVOLUTION   OF   LIFE 

which  enables  these  animals  to  feed  practically  in  the  same 
manner  as  the  raptorial  birds. 

Herbivorous  Dinosaurs,  Sauropoda 

As  analyzed  by  Lull  along  the  lines  of  modern  interpreta- 
tion,  beside   the   small  carnivorous  dinosaurs    there    may   be 

traced   in   the   Connecticut 
Triassic  footprints    the  be- 
ginnings of  an  herbivorous 
offshoot    of    the    primitive 
carnivorous  dinosaur  stock, 
leading  into  the  elephantine 
types  of  herbivorous  dino- 
saurs known  as  the  Sauro- 
poda,  which    were    first 
brought   to  our  knowledge 
in  this  country  through  the 
pioneer    studies    of    Marsh 
and  Cope. 

As  there  is  never  any 
need  of  haste  in  the  capture 
of  plant  life  these  animals 
underwent  a  reversed  evo- 
lution of  the  limbs  from  the 
swift-moving  primitive  bi- 
pedal type  into  a  secon- 
dary slow-moving  quadru- 
pedal ambulatory  type. 
The  original  power  of  occa- 
sionally raising  the  body 
on  the  hind  limbs  was  still  retained  in  some  of  these  gigantic 
forms.      The    half-way    stage  between    the    bipedal    and    the 


TRIASSIC 


ANCHISAURUS 
REPTILIA 

Fig.  94.  Analogy  Between  the  Carnivo- 
rous Anchisaurus  Type  of  the  Triassic 
AND  the  Ancestral  Herbivorous  Sauro- 
POD  Type  Platcosauriis. 

The  upper  restoration  {Plateosaiirus)  repre- 
sents a  bipedal  stage  of  sauropod  evolution 
which  was  discovered  in  the  German  Trias, 
in  which  the  transition  from  carnivorous  to 
herbivorous  habits  is  observed.  Recent 
discovery  renders  it  probable  that  the 
herbivorous  Sauropoda  descend  from  carniv- 
orous ancestors  like  Anchisaurus. 

Restoration  of  Plateosaiirus  modified  from  Jae- 
kel.     Restoration  of  Anchisaurus  after  Lull. 


HERBIVOROUS   DINOSAURS 


217 


' 


quadrupedal  mode  of  progression  is  revealed  in  the  recently 
described  Plateosaurus  of  Jaekel  from  the  Trias  of  Germany 
(Fig.  94),  an  animal  which  could  progress  either  on  two  or  on 

four  legs. 

The  Sauropoda  reached  the  climax  of  their  evolution  dur- 
ing the  close  of  Jurassic   (Morrison  formation)   and  the  be- 


DEPOSITS  g;  CONTINENTAL  DEPOSITS 


VEIANG1AN-HIUS-WEALDEN.TRINITY.M0RISS0N)TIME 


.  MARINE 


^ 


SIEHKA  NEVADA 


Fig   OS     Theoretic  World  Environment  in  Lo^-er  Cretaceous  Time. 

The  dominant  period  of  the  great  sauropod  dino^urs.    '^'^'-^.^^/^^^^'j^^tL'ltc 
Atlantic  continent  Gondwana  connecting  South  America  and  Africa,  and  the  fcurasiatic 

MedUerranein  sea  Tcthys.    Shortly  afterward  comes  the  rise  of  the  modern  flowering 
Med  terranean  ^ea  .J   y  >  ^^^^  ^^^  ^^j^^.^g  ^^^,„„  of  Wyo- 

S -1  Color'a^oTt^e  Slain  (Morrison)'centre  of  the  giant  Sauropoda  (see  Fig. 
97).     After  Schuchert,  1916. 

ginning  of  Cretaceous  time  (Comanchean  Epoch).  Meanwhile 
they  attained  world-wide  distribution,  migrating  throughout  a 
long  stretch  of  the  present  Rocky  Mountain  region  of  North 
America,  into  southern  Argentina,  into  the  Upper  Jurassic  of 
Great  Britain,  France,  and  Germany,  and  into  eastern  Africa. 
The  last  named  region  is  the  one  most  recently  explored,  and 


2l8 


THE  ORIGIN  AND   EVOLUTION  OF   LIFE 


HERBIVOROUS   DINOSAURS 


219 


the    widely    heralded  Giganlosauriis    (^=  Bracliiosaiiriis) ,  de- 
scribed  as   the   largest  land-living  vertebrate   ever  found,   is 


Fio.  96.    North  America  in  Lower  Cretaceous  (Comanchian)  Time. 

This  period,  also  known  as  the  Trinity-Morrison  time,  is  marked  by  the  maximum  develop- 
ment of  the  giant  herbivorous  dinosaurs,  the  Sauroixxia.  The  Sierra  Nevada  and  coast 
ranges  are  elevated,  also  the  mountain  ranges  of  the  Great  Basin  which  give  rise  east- 
ward to  the  flood-plain  deposits  (Morrison)  in  which  the  remains  of  the  Sauropoda  are 
entombed.  This  epoch  is  prior  to  the  birth  of  the  Rocky  Mountains,  which  arose  be- 
tween Cretaceous  and  Eocene  time.  Detail  from  the  globe  model  in  the  American 
Museum  by  Chester  A.  Reeds  and  George  Robertson,  after  Schuchert. 

Structurally  closely  related  to  and  does  not  exceed  in  size  the 
sauropods  discovered  in  the  Black  Hills  of  South  Dakota. 
Their  size  is  indeed  titanic,  the  length  being  100  feet,  while  the 


longest  whales  do  not  exceed  90  feet.  In  height  these  sauropods 
dwarf  the  straight-tusked  elephant  of  Pleistocene  time,  which 
is  the  largest  land  product  of  mammalian  evolution.  The 
Sauropoda  for  the  most  part  inhabited  the  swampy  meadows 
and  flood-plains  of  Morrison  time.     They  include,  besides  the 


BRACHIOSAURUS 


BCPTIUA 


CRETACEOUS 


0«PUWOCUS 


nVTKJA 


JURA- 
CRETACEOUS 


CAMARASAURUS 


REPTILIA 


JURA- 
CRETACEOUS 


Fig.  97.    Tkrle  1  rincipal  Types  cf  Sauropods. 

The  body  form  of  the  three  principal  types  of  giant  herbivorous  Sauropoda  which  ap- 
near  to  have  been  almost  world-wide  m  distribution.  ^.  ,   ,  ,•  v,f 

C-ri  :«r,.,   a  heavy-bodied,   short-limb^  quadrupedal  type,    ^f  f -'^^^.^^f^' 
bodicd    relatively  swift-moving  quadrupedal   type.     Bra<:hvosmm,s,   a   ^hort-bodied 
aTadrupSal  tyii  in  which  the  fore  limbs  are  more  elevated  than  the  hmd  l.mbs. 
S)r.l  Gained  gigantic  size,  being  related  to  the  recently  discovered  Gt.arUo- 
saurus  of  East  Africa.     Restorations  by  Osbom,  Matthew,  and  Deckert. 

gigantic  type  Brachiosaurus  {=  Gigantosaurus),  with  its  greatly 
elevated  shoulder  and  forearm,  massive  quadrupedal  types  like 
Camarasaurus  Cope  and  Apatosaurus  (  -  Bronlosaurus)  Marsh, 
and  the  relatively  long,  slender,  swiftly  moving  Diplodocus. 
According  to  Lull  and  Deperet  the  Sauropoda  survived  until 
the  close  of  the  Cretaceous  Epoch  in  Patagonia  and  in  southern 
France.  In  North  America  they  became  extinct  in  Lower 
Cretaceous  time. 


220 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


In  the  final  extinction  of  the  herbivorous  sauropod  type  we 
find  an  example  of  the  selection  law  of  elimination,  attributable 


Fig.  98.    Amphibious  or  Terrestrio-Fluviatile  Theory  of  the  Habits  of 

Apatosaurus. 
(Upper.)     Apatosaurus   {^Broutosaurus),  a  typical  sauropod  of  Morrison  age    quad- 
rupedal, heavy-limbed,  herbivorous,  inhabiting  the  flood-plains  (Morrison)  and  lagoons 
of  the  region  now  elevated  into  the  Rocky  Mountain  chain  of  Wyoming  and  Colorado. 
<Lower.)     Mounted  skeleton  of  Apatosaurus  {  =  Brontosaurus)  in  the  American  Museum 
of  Natural  History. 

to  the  fact  that  these  types  had  reached  a  cul-de-sac  of  mechan- 
ical evolution  from  which  they  could  not  adaptively  emerge 


HERBIVOROUS  DINOSAURS 


221 


when  they  encountered  in  all  parts  of  the  world  the  new  en- 
vironmental conditions  of  advancing  Cretaceous  time. 


The  Iguanodontia 


Contemporaneous  with  the  culminating  period  of  the  evo- 
lution of  the  Sauropoda  is  the  world-wide  appearance  of  an 


J  f^ 


Fig.  99.    Primitive  Iguanodont  Camptosaurus  from  the  Upper  Jurassic  of 

Wyoming. 

This  swift  bipedal  form  was  contemporary  with  the  giant  sauropod  Apatosaurus  and  the 
liKhter-bodied  Diplodocus.  These  iguanodonts  were  defenseless  and  dependent  wholly 
on  alertness  and  speed,  or  perhaps  on  resort  to  the  water,  for  escape  from  their  enem.es. 
They  were  the  prey  of  Allosaurus  (see  Fig.  91)-  Mounted  specimen  m  the  American 
Museum  of  Natural  History. 

entirely  different  stock  of  bipedal  herbivorous  dinosaurs  in 
which  the  pelvis  is  bird-like  (Ornithischia,  Seeley).  These 
animals  may  be  traced  back  (von  Huene)  to  the  Triassic 
Naosaurus.  The  front  of  the  jaws  at  an  early  stage  lost  the 
teeth  and  developed  a  horny  sheath  or  beak  like  that  of  the 
birds,  within  which  a  new  bone  (predentary)  evolves,  giving  to 
this  order  the  name  Predentata.  Entirely  defenseless  at  this 
stage   {Camptosaurus),   these   relatively   small,   bipedal   types 


222 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


Fig.  ioo.    A  Fair  of  Upper  l^retaceous  Iguano- 

DONTS   FROM   MONTANA. 

After  a  lapse  of  500,000  years  of  Cretaceous  time  the 
Camptosaurus  (Fig.  qq)  evolved  into  the  giant  "  duck- 
billed" dinosaur  Trachodon,  described  by  Leidy  and 
Cope  from  the  Upper  Cretaceous  of  New  Jersey  and 

Dakota. 
Two  skeletons  of  Trachodon  annedens  (upper)  discovered 
in  Montana,  as  mounted  in  the  American  Museum  of 
Natural  History,  and  restoration  of  the  same  (lower) 
by  Osborn  and  Knight.     (Compare  Fig.  74-) 


spread   all   over   the 
northern    hemisphere 
and  attained  an  extra- 
ordinary adaptive  radi- 
ation in  the  river-  and 
shore -living    ''duck- 
biir*  dinosaurs,   the 
iguanodonts  of  the  Cre- 
taceous Epoch  (Fig. 
loi).      The  adaptive 
radiation  of  these  ani- 
mals has  only  recently 
been  fully  determined; 
it  led  into  three  great 
t>pes  of  body  form,  all 
unarmored.     First,  the 
less  specialized  types 
which   retain    more    or 
less  the  body  structure 
of   the   earlier  Jurassic 
forms  and   the  famous 
iguanodont    of    Bernis- 
sart,  Belgium.     Related 
to  these  are  the  krito- 
saurs  of  the  Cretaceous 
of  Alberta,  with  a  com- 
paratively narrow  head, 
the  protection  of  which 
was    facilitated    by    a 
long,   backwardly    pro- 
jecting spine.     Second, 
there    are    the    broadly 


HERBIVOROUS   DINOSAURS 


223 


duck-billed,  wading  dinosaurs  {Trachodon),  with  stalking  Umbs 
and  elevated  bodies.  Third,  there  are  more  fully  aquatic,  free- 
swimming    forms    with    crested   skulls    {Corythosaurus).     The 


^'i  ■'  V 


**>«*^'S*fi^>w*»f}!«»>i' 


Fig.  ioi.    Adaptive  Radiation  of  the  Iguanodont  Dinosaurs  into  Three  Groups. 

(Upper.)  Three  characteristic  types:  A,  Typical  "duck-bill"  Trachodon;  B,  Corytho- 
saurus, the  hooded  "duck-bill,"  with  a  head  like  a  cassowary,  probably  aquatic;  C, 
Kritosaurus,  the  crested  "duck-bill  "  dinosaur.     Restorations  by  Brown  and  Deckert. 

(Lower.)  Mounted  skeleton  of  Corythosaurus  in  the  American  Museum  of  Natural  His- 
tory, recenUy  discovered  in  the  Upper  Cretaceous  of  Alberta,  Canada,  with  the  integ- 
ument impressions  and  body  lines  preserved. 

anatomy  and  habits  of  all  these  forms  have  been  made  known 
recently  by  American  Museum  explorations  in  Alberta,  Canada, 
under  Barnum  Brown  (Fig.  loi). 

The   partly   armored   dinosaurs   known   as   stegosaurs  are 
related  to  the  iguanodonts  and  belong  to  the  bird-pelvis  group 


\ 


224  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

(Ornithischia).  The  small  Triassic  ancestors  of  this  great 
group  of  herbivorous,  ornithischian  dinosaurs  also  gave  rise 
to  a  number  of  secondarily  quadrupedal,  slow-moving  forms, 
in  which  there  developed  various  forms  of  defensive  and  offen- 
sive armature.  Of  these  the  Jurassic  stegosaurs  exhibit  a 
reversed  evolution  in  their  locomotion  since  they  pass  from  a 
bipedal  into  a  quadrupedal  type  in  which  the  armature  takes 


v/^pmm^"-  \ .. 


Fig.  I02.    Offensive  and  Defensive  Energy  Complexes. 
The  carnivorous  "tyrant"  dinosaur  Tyrannosaurus  approaching  a  group  of  the  homed 

herbTorous  dinoLrs  known  as  Ceratopsia.     Compare  frontispiece. 
Th.  reratoDsia  are  related  to  the  armored  Slegosaurns  and  to  the  armorless,  sw.  t-movmg 
^  IguanXntra.    R^toration  by  Osbom  in  the  American  Museum  of  Natural  H.story. 

painted  by  Charles  R.  Knight. 

the  form  of  sharp  dorsal  plates  and  spiny  defenses,  the  exact 
arrangement  of  which  has  been  recently  worked  out  by  Gil- 
more  Doubtless  when  this  animal  was  attacked  it  drew  its 
head  and  limbs  under  its  body,  like  the  armadillo  or  porcu- 
pine  and  relied  for  protection  upon  its  dorsal  armature,  aided 
by  rapid  lateral  motions  of  the  great  spines  of  the  tail  to  ward 
off  its  enemies.  During  the  progress  of  Cretaceous  time  these 
stegosaurs  became  extinct,  and  by  the  beginning  of  the  ^Iiddle 
Cretaceous  two  other  herbivorous  types  are  given  off  from  the 

predentate  stock. 

The   first   of   these   are   the   aggressively   and   defensively 
horned  Ceratopsia,  in  which  two  or  three  front  horns  evolved 


HERBIVOROUS  DINOSAURS 


225 


step  by  step,  with  a  great  bony  frill  protecting  the  neck.     This 
evolution  took  place  stage  by  stage  with  the  evolution  of  the 
predatory    mechanism   of  the  carnivorous  dinosaurs,  so  that 
the   climax  of  ceratopsian  defense  {Triceratops)  was  reached 
simultaneously  with  the  cUmax  of  Tyrannosaurus  offense.    This 
is  an  example  of  the  counteracting  evolution  of  offensive  and 
defensive  adaptations,   analogous  to  that  which  we  observe 
to-day  in  the  evolution  of  the  lions,  tigers,  and  leopards,  which 
counteracts  with  that  of  the  horned  cattle  and  antelopes  of 
Africa,  and  again  in  the  evolution  of  the  wolves  simultaneously 
with  the  horned  bison  and  deer  in  the  northern  hemisphere. 
It  is  a  case  where  the  struggle  for  existence  is  very  severe  at 
every  stage  of  development  and  where  advantageous  or  dis- 
advantageous chromatin  predispositions  in  evolution  come  con- 
stantly under  the  operation  of  the  law  of  selection.     Thus  in  the 
balance  between  the  reptilian  carnivora  and  herbivora  we  find 
a  complete  protophase  of  the  more  recent  balance  between  the 
mammalian  carnivora  and  herbivora. 

The  climax  of  defense  was  reached,  however,  in  another 
line  of  Predentata,  in  the  herbivorous  dinosaurs,  known  as 
Ankylosaurus,  in  which  there  developed  a  close  imitation  of  the 
armadillo  or  glyptodon  type  of  mammal,  with  the  head  and 
entire  body  sheathed  in  a  very  dense,  bony  armature.  In 
these  animals  not  only  is  motion  abandoned  as  a  means  of 
escape,  but  the  teeth  become  diminutive  and  feeble,  as  in  most 
other  heavily  armored  forms  of  reptiles  and  mammals.  The 
herbivorous  function  of  the  teeth  is  replaced  by  the  develop- 
ment of  horny  beaks.  Thus  these  animals  reach  a  ground- 
dwelling,  slow-moving,  heavily  armored  existence. 


2  26  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

Pterosaurs 
There  is  no  doubt  that  the  pterosaurs,  flying  reptiles,  were 
adapted  to  fly  far  out  to  sea,  for  their  remains  are  found  min- 
gled with  those  of  the  mosasaurs  in  deposits  far  from  the 
ancient  shore-lines.  There  is  no  relation  whatever  between 
the  feathered  birds  and  these  animals,  whose  analogies  in  their 
modes  of  flight  are  rather  with  the  bats  among  the  mammals. 

These  flying  reptiles  are 
perhaps  the  most  extraor- 
dinary of  all  extinct  ani- 
mals.    While  some  ptero- 
saurs were    hardly    larger 
than  sparrows,  others  sur- 
passed all  living  birds  in 
the    spread  of   the  wings, 
although  inferior  to  many 
birds  in    the    bulk  of  the 
body.     It  is  believed  that 
they  depended  almost  entirely  upon  soaring  for  progression. 
The  head  in  the  largest  types  of  the  family  (Pteranodon)  is 
converted  into  a  great  vertical  fin,  used,  no  doubt,  in  directing 
flight,  with  a  long,  backwardly  projecting  bony  crest  which 
served  in  the  balancing  of  the  elongate  and  compressed  bill. 
The  feeble  development  of  the  muscles  of  flight  in  these  an- 
cient forms  is  compensated  for  by  the  extreme  lightness  of  the 
body  and  the  hullowness  of  the  bones. 

Origin  of  Birds 

It  is  believed  that  in  late  Permian  or  early  Triassic  time  a 
small  lizard-like  reptile  of  partly  bipedal  habit  and  remotely 
related  to  the  bipedal  ancestors  of  the  dinosaurs  passed  irom 


Fig.  103.    Restoration  of  the  Pterodactyl, 
Showing  the  Soaring  Flight. 

After  the  Aeronautical  Journal,  London. 


ORIGIN  OF  BIRDS 


227 


a  terrestrial  into  a  terrestrio-arboreal  mode  of  life,  probably 
for  purposes  of  safety.  This  early  arboreo-terrestrial  phase  is 
indicated  in  the  most  ancient  known  birds  (Archceopteryx)  by 
the  presence  of  claws  at  the  ends  of  the  bones  of  the  wing,  fit- 
ting them  for  clinging  to  trees,  it  is  argued,  through  analogy 
to  the  tree-clinging  habits  of  existing  young  hoatzins  of  South 


QOOTEWNARY 


TCimARV 


UPPER 
CRETACEOUS 


LOWER 
CRETACEOUS 
IC  OMANCHCAN) 


JURASSIC 


TRIASSiC 


PENNSYLVANIAN 
CAHSONIFCmSUSI 


MISSISSIPPIAN 

<Lowr» 
CAitaoNirrnous 


FUGHTLESS  RUNNING  BIROS 


MODERNIZED  BIRDS 


TOOTHED  DIVERS 


PRIMITIVE  TOOTHED  BIRDS 


.7  FIRST  RADIATION  FROM  ARBOREAL  INTO 
TERRESTRIAL  AND  AQUATIC  BIRDS 


r 


ARBOREAL  BIRDS  OF  FEEBLE  FLIGHT  lARCHAEOPTERYXI 


'^ 


T  FIRST  aiROS-BtPEDAL.  CURSORIAL  CLIMBING  IHIGH  BODY  TEMP, 
RELATIVELY  HIGH  REPTILIAN  BRAINI 


COMMON  ANCrSTORS  OF  CROCODILES.  PHYTOSAURS. 
DINOSAURS.  PTEROSAURS  AND  BIRDS  _ 


ORIGIN  AND  ADAPTIVE  RADIATION  OF  THE  BIRDS 


W    K   GREOOHY    l»l« 


Fig.  104.  Ancestral  Tree  of  the  Birds. 
The  ancestors  of  the  birds  branch  off  in  Permian  time  from  the  same  stock  that  gives  rise 
to  the  dinosaurs,  adding  to  swift,  bipedal  locomotion  along  the  ground  the  power  of 
tree  climbing  and,  with  their  very  active  life,  the  development  of  a  high  and  uniform 
body  temperature.  Primitive  types  of  birds  exhibit  a  fore  limb  terminating  in  claws, 
probably  for  grasping  tree  branches.  The  power  of  flight  began  to  develop  in  Triassic 
time  through  the  conversion  of  scales  into  feathers  either  on  the  fore  limbs  (two-wing 
theor>')  or  on  both  fore  and  hind  limbs  (four-wing  theory).  From  the  Jurassic  birds 
(ArcluEoplcryx),  capable  of  only  feeble  flight,  there  arises  an  adaptive  radiation  into 
aerial,  arboreal,  arboreo-terrestrial,  terrestrial,  and  aquatic  forms,  the  last  exhibiting  a 
reversal  of  evolution.     Diagram  prepared  for  the  author  by  W.  K.  Gregory. 

America.  Ancestral  tree  existence  is  rendered  still  more  prob- 
able by  the  fact  that  the  origin  of  flight  was  apparently  sub- 
served in  the  parachute  function  of  the  fore  limb  and  perhaps 
of  both  the  fore  and  hind  limbs  for  descent  from  the  branches 
of  trees  to  the  ground. 

Two  theories  have  been  advanced  as  to  the  origin  of  flight 
in  the  stages  succeeding  the  arboreal  phase  of  bird  evolution. 
First,  the  pair-idng  theory,  developed  from  the  earlier  studies 
on  Archccopteryx,  in  which  the  transformation  of  lateral  scales 


I 


Fig.    io- 


Skeleton  of  Archaopteryx 
(left)  Compared  with  That  of  the 
Pigeon  (right). 
Showing  the  abbreviation  of  the  tail  into 
the  pygostyle  and  the  conversion  of 
the  grasping  fore  limb  into  the  bones 
of  the  wing.     After  Heilman. 


228  THE  ORIGIN  AND  EVOLUTION  OE  LIEE 

into  long  primary   feathers  on 
the  fore  limbs  and  at  the  sides 
of  the  extended  tail  would  afford 
a    glissant    parachute    support 
for  short  flights  from  trees  to 
the  ground   (Fig.  106).     Quite 
recently  a  Joiir-uing  theory,  the 
tetrapteryx  theory,  has  been  pro- 
posed by  Beebe,  based  on  the 
observation  of  the  presence  of 
great  feathers  on  the  thighs  of 
embryos  of   modern  birds  and 
of  supposed  traces  of  similar  feathers  on  the  thighs  of  the  old- 
est  known  fossil  bird,  the  Ar- 
chcFOpteryx  of  Jurassic  age.    Ac- 
cording to  this  hypothesis  after 
the  four-wing  stage  was  reached 
the  two  hind-leg  wings  degen- 
erated   as    the    flight    function 
evolved  in  the  spreading  feathers 
of   the   forearm-wings  and   the 
rudder  function  was  perfected 
in  the  spreading  feathers  of  the 
tail  (Fig.  107).     Both  of  these 


Fig.    106.    Silhouettes    of    Archaop- 

teryx  (A)  and  Pheasant  (B). 

Based  on   the   two-wing   theory.     After 

Heilman. 


</ 


>>.'/. 


' '  '*/ 


"<ui.i/  Ljj->**^ 


.„-••:^^*'^ 


Fig.  107.    Four  Evolutionary  Stages  in  the  Hypothetical  Four-winced  Bird. 

After  Beebe. 


ORIGIN  OE   BIRDS 


229 


r 


h>T)Otheses  assign  two  phases  to  the  origin  of  flight  in  birds: 

first,  a  primary  terrestrial  phase,  during  which  the  peculiar 

characters  of   the  hind  limbs 

and  feet  were  developed  with 

their  strong   analogies  to  the 

bipedal  feet  of  dinosaurs; 

second,  a  purely  arboreal 

phase.     It  is  believed  by  the 

adherents    of    both    the   two- 


Fig.  108.  Theoretic  Mode  of  Para- 
chute Flight  of  the  Primitive 
Bird. 

Based  on  the  four-wing  theory.     After 
Beebe. 

wdng  and  the  four- wing  theory 
that    following   the   arboreal 
phase,  in  which  the  powers  of 
flight   were  fully   developed, 
there  occurred  among  the 
struthious  birds,  such  as  the 
ostriches,  a  secondary  terres- 
trial phase  in  which   the 
powers  of  flight  were  secon- 
darily lost  and  rapid  cursorial 
locomotion  on  the  ground  was 
secondarily  developed.     This 
interpretation  of  the  foot  and 
limb    structure    associated 
with  the  loss  of  teeth,  which 
is  characteristic  of  all  the  higher  birds,  will  explain  the  close 
analogies  which  exist  between  the  ostrich-like  dinosaur  Stru- 


FiG.  109.    Restoration  of  the  Ancient 
Jurassic  Bird,  ArchcEoptcryx. 

Capable  of   relatively   feeble   flight.    After 

Heilman. 


\ 


230  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

thiomitnus  and  the  modern  cursorial  flightless  forms  of  birds, 
such  as  the  ostriches,  rheas,  and  cassowaries. 

In  the  opposite  extreme  to  these  purely  terrestrial  forms, 
the  flying  arboreal  birds  also  gave  off  the  water-living  birds, 
one  phase  in  the  evolution  of  which  is  represented  in  the  loon- 
like Hesperomis,  the  companion  of  the  pterosaurs  and  mosa- 
saurs  in  the  Upper  Cretaceous  seas.     It  was  on  the  jaws  of  the 


Fig.  1 10.  Reversed  Aquatic  Evolution  of  Wino  and  Body  Form. 
Wine  of  a  oenguin  (.4)  transformed  into  a  fin  externally  resemblini?  the  f^n  of  a  shark  (B). 
Sk^Lo^'lcserLs  (C)  in  the  .American  Museum  of  Natural  History  and  restora- 
tion of  Ilcspcrorms  (D)  by  Heilman,  both  showing  the  transformation  of  the  lly.n«  b.rd 
into  a  swimming,  aquatic  type,  and  its  convergent  evolution  toward  the  body  shape  of 
the  shark,  ichthyosaur,  and  dolphin  (compare  tig.  41)- 

Hesperomis  and  smaller  Ichlhyornis  that  Marsh  made  his  sen- 
sational announcement  of  the  discovery  of  birds  with  teeth, 
a  discovery  confirmed  by  his  renewed  studies  of  the  classic 
fossil  bird' type,  the  Jurassic  Archccopteryx.     These  divers  of 
the  Cretaceous  seas  {Hesperomis)  are  analogous  to  the  modern 
loons,  and  represent  one  of  the  many  instances  in  which  the 
tempting  food  of  the  aquatic  habitat  has  been  sought  by  ani- 
mals venturing  out  from  ihc  shore-lines.     As  in  the  most  highly 
specialized  modern  swimming  birds,   the  Antarctic  penguins, 
the  wing  secondarily  evolves  into  a  fm  or  paddle,  while  the 


ARRESTED   REPTILIAN  EVOLUTION 


231 


.4 


«> 


body  secondarily  develops  a  fusiform  shape  in  order  to  dimin- 
ish resistance  to  the  water  in  rapid  swimming. 

Possible  Causes  of  the  Arrested  Evolution  of  the 

Reptiles 

Of  the  eighteen  great  orders  of  reptiles  which  evolved  on 
land,  in  the  sea,  and  in  the  air  during  the  long  Reptilian  Era 
of  ii,ooo,ooo  years,  only  five  orders  survive  to-day,  namely, 
the  turtles  (Testudinata),  tuateras  (Rhynchocephalia) ,  lizards 
(Lacertilia),  snakes  (Ophidia),  and  crocodiles  (Crocodilia). 

The  evolution  of  the  members  of  these  five  surviving  or- 
ders has  either  been  extremely  slow  or  entirely  arrested  during 
the  3,000,000  years  which  are  generally  assigned  to  Tertiary 
time-  we  can  distinguish  only  by  relatively  minor  changes  the 
turtks  and  crocodiles  of  the  base  of  the  Tertiary  from  those 
living  to-day.     In  other  words,  during  this  period  of  3,000,000 
years  the  entire  plant  world,  the  invertebrate  world,  the  fish, 
the  amphibian,   and  the  reptilian  worlds  have  all  remained 
as  relatively  balanced,  static,  unchanged  or  persistent  types, 
while  the  mammals,  radiating  3,000,000  years  ago  from  very 
small  and  inconspicuous  forms,  have  undergone  a  phenomenal 
evolution,    spreading   into   every   geographic   region   formerly 
occupied  by  the  Reptilia  and  passing  through  multitudinously 
varied  phases  not  only  of  direct  but  of  alternating  and  of 
reversed  evolution.     During  the  same  epoch  the  warm-blooded 
birds  were  doubtless  evoh-ing,  although  there  are  relatively 
few  fossil  records  of  this  bird  evolution. 

This  is  a  most  striking  instance  of  the  differences  in  chroma- 
tin potentiality  or  the  internal  evolutionary  impulses  under- 
lying all  X  isible  changes  of  function  and  of  form.  If  we  apply 
our  law  of  the  actions,  reactions,  and  interactions  of  the  four 
physicochcmical  energies  (p.   21),  there  are  four  reasons  why 


illl 


1 


232 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


we  may  not  attribute  this  relatively  arrested  development  of 
the  reptiles  either  to  an  arrested  physicochemical  environment, 
to  an  arrested  life  environment,  or  to  the  relative  bodily  iner- 
tia of  reptiles  which  affects  the  body-protoplasm  and  body- 
chromatin.     These  four  reasons  appear  to  be  as  follows: 

First:  We  have  noted  that  among  the  reptiles  the  velocity 
of  purely  mechanical  adaptation  is  quite  independent  both  of 
brain  power  and  of  nervous  activity,  a  fact  which  seems  to 
strike  a  blow  at  the  psychic-direction  hypothesis  (p.  143),  on 
which  the  explanations  of  evolution  by  Lamarck,  Spencer,  and 
Cope  so  largely  depend.  The  law  that  perfection  of  mechan- 
ical adaptation  is  quite  independent  of  brain  power  also  holds 
true  among  the  mammals,  because  the  small-brained  mammals 
of  early  Tertiary  time,  the  first  mammals  to  appear,  evolve  as 
mechanisms  quite  as  rapidly  or  more  rapidly  than  the  large- 
brained  mammals. 

Second:  The  law  of  rapidity  of  character  evolution  is  inde- 
pendent also  of  body  temperature,  for,  while  the  mechanical 
evolution  of  the  warm-blooded  birds  and  mammals  is  verv 
rapid  and  very  remarkable  it  can  hardly  be  said  to  have  ex- 
ceeded that  of  the  cold-blooded  reptiles.  Thus  the  causes  of 
the  velocity  of  character  evolution  in  mechanism  need  not  be 
sought  in  the  psychic  influence  of  the  brain,  in  the  nervous 
system,  in  the  ^^Lamarckian''  influence  of  the  constant  exer- 
cise of  the  body,  nor  in  a  higher  or  lower  temperature  of  the 
circulatory  system. 

Third:  Nor  has  the  relatively  arrested  evolution  of  the 
Reptilia  during  the  period  of  the  Age  of  Mammals  been  due 
to  arrested  environmental  conditions,  for  during  this  time  the 
environment  underwent  a  change  as  great  as  or  greater  than 
that  during  the  preceding  Age  of  Reptiles. 

Fourth,  and  finally,  there  is  no  evidence  that  natural  selec- 


ARRESTED   REPTILIAN  EVOLUTION 


233 


tion  has  exerted  less  influence  on  reptilian  evolution  during  the 
Age  of  Mammals  than  previously.  Thus  we  shut  out  four  out 
of  five  factors,  namely,  physical  environment,  individual  habit 
and  development,  life  environment,  and  selection  as  reasonable 
causes  of  the  relative  arrest  of  evolution  among  the  reptiles. 

Consequently  the  causes  of  the  arrest  of  evolution  among 
the  Reptilia  appear  to  lie  in  the  internal  heredity-chromatin, 
i.  €.,  to  be  due  to  a  slowing  down  of  physicochemical  inter- 
actions, to  a  reduced  activity  of  the  chemical  messengers  which 
theoretically  are  among  the  causes  of  rapid  evolution. 

The  inertia  witnessed  in  the  entire  body  form  of  static  or  per- 
sistent types  is  also  found  to  occur  in  certain  single  characters 
of  the  individual.  Recurring  to  the  view  that  evolution  is  in 
part  the  sum  of  the  acceleration,  balance,  or  retardation  of 
the  velocity  of  single  characters,  the  five  surviving  orders  of 
the  reptiles  appear  to  represent  organisms  in  which  the  greater 
number  of  characters  lost  their  velocity  at  the  close  of  the 
Age  of  Reptiles,  and  consequently  the  order  as  a  whole  re- 
mained relatively  static. 


I 


CHAPTER  VIII 
EVOLUTION  OF  THE  MAMMALS 

First  mammals,  of  insectivorous  and  tree-living  habits.  Single  character 
evolution,  physicochemical  interaction,  coordination,  and  complexity. 
Problem  as  to  the  causes  of  the  origin  of  new  characters  and  of  new 
bodily  proportions.  Adaptations  of  the  teeth  and  of  the  limbs  as  observed 
in  direct,  reversed,  alternate,  and  counteracting  evolution.  Physiographic 
and  climatic  environment  during  the  period  of  mammalian  evolution,  in  a 
measure  deduced  from  adaptive  variations  in  teeth  and  feet  of  mammals. 
Conclusions,  present  knowledge  of  biologic  evolution  among  the  verte- 
brate animals.  Future  lines  of  inquiry  into  the  causes  of  evolution. 

It  required  a  man  of  genius  like  Linnaeus  to  conceive  the 
inclusion  within   the  single  class   Mammalia  of   such  diverse 


Fig.  III.    The  Sex  Whale,  Bal.«noptera  Borealis, 

Which  attains  a  total  length  of  forty-nine  feet.     Restoration  (upper)  and  photograph 

(lower)  after  Andrews. 

forms  as  the  tiny  insect-loving  shrew  and  the  gigantic  preda- 

ceous  whale.     It  has  required  one  hundred  and  twenty-five 

years  of  continuous  exploration  and  research  to  establish  the 

fact  that  the  whale  type   (Fig.  iii),  is  not  only  akin  to  but 

234 


ORIGIN  OF  MAMMALS 


23s 


I 


is   probably   a   remote    descendant  of   an   insectivorous   type 
not  very  distant  from  the  existing  tree  shrews  (Fig.  112),  the 

transformation  of  size,  of  func- 
tion, and  of  form  between  these 
two  extremes  having  taken 
place  within  a  period  broadly 
estimated  in  our  geologic  time 
scale  at  about  10,000,000 
years. 


Fig.  112.    The   Tree  Shrew  Tupaia. 
Insectivore,  considered  to  be  near  the  pro- 
totype form  of  all  the  higher  placental 
mammals. 

Origin  of  the  Mammals,  Insec- 
tivorous, Arboreal 

To  the  descent  of  the  mammals 
Huxley  was  the  first,  in  essaying  the 
reconstruction  of  the  great  ancestral 
tree,  to  apply  Darwin's  principles 
on  a  large  scale  and  to  prophesy 
that  the  very  remote  ancestral 
form  of  all  the  mammals  was  of  an 
insectivore  type.  Subsequent  re- 
search^ has  all  tended  in  the  same 
direction,  pointing  to  insectivorous 
habits  and  in  many  ways  to  arboreal 
modes  of  existence  as  characteristic 


Fig.  113.  Primitive  Types  of 
monotreme  and  marsupial. 

(Below.)  Monotreme  type — Echid- 
na, the  spiny  ant-eater. 

(Above.)  Marsupial  type — Didcl- 
phys,  the  arboreal  opossum  of 
South  America.  After  photo- 
graphs of  specimens  in  the  New 
York  Zoological  Park. 


'This  insectivorous  and  tree-inhabiting  theory  of  mammalian  origin  has  recently 
been  advocated  by  Doctor  William  Diller  Matthew  of  the  American  Museum  of  Natural 
History,  by  Doctor  William  K.  Gregory  of  Columbia  University  (''The  Orders  of  Mam- 
mals"), and  Doctor  Elliot  Smith  of  the  University  of  Glasgow. 


236  THE  ORIGIN  AND   EVOLUTION  OF   LIFE 

of  the  earliest  mammals.  Proofs  of  arboreal  habit  are  seen  in 
the  limb-grasping  adaptations  of  the  hind  foot  in  many  prim- 
itive mammals,  and  even  in   the  human  infant.     Thus   the 


0: 


PLllSTOCEne 


PUOCENt 


WMAHS       M»L»    C«l»<iVCX<t«         1NMCTVOM1    MTS 


> 

a. 

< 
P 

K 
U 

l- 


OLIOOCCNE 


ft 


OmeiN  ANO  ADAPTIVt  PACHATTON  QT  TMC  MAMMALS 

lOOT' 

n 


«r  K  •acooarr  ww 


U 

O 

N 

Ul 


PALCOCCNC 


INWCTI  "^^^ 


CBETACEOU* 


LOWC« 
CRETACEOUS 
<OMANCMCAM 


4STM»oroir» 


.y 


VAOICO 


i 


CAIINIVONCS 


JURASSIC 


CARBONIFEROUS 


Fig.  114.    Ancestral  Tree  of  the  Mammals. 

Adaptive  radiation  of  the  xMammalia,  originating  from  Triassic  ^^^^f^^^.J^^t^^^,^^ 
dividing  into  three  main  branches:  {A)  the  primitive,  egg-laymg,  reptile-  ike  mammals 
(Monotremes);  {B)  the  intermediate  pouched,  viviparous  mammals  (Marsupials- 
orissums  etc  );  and  (C)  the  true  Placental  which  branch  off  from  small  primitive 
ad^'eo  insectivorous  forms  (Trituberculata)  of  late  Triassic  time  into  the  four  grand 
divisions  (i)  the  clawed  mammals,  (2)  the  Primates,  (3)  the  hoofed  mammals,  and  (4) 
the  cetaceans.  Dividing  into  some  thirty  orders,  this  grand  evolution  and  adaptive 
radiation  takes  place  chiefly  during  the  four  million  years  of  Upper  Cretaceous  and 
Tertiary  time.  As  among  the  Reptilia,  the  primary  arboreo-terrestrial  adaptive  phases 
radiate  hv  direct  evolution  into  all  the  habitat  zones,  and  by  reverscd^nd  alternate  evolu- 
tion  develop  backward  and  forward  in  adaptation  to  one  or  another  habitat  zone.  Dia- 
gram prepared  for  the  author  by  W.  K.  Gregory. 

existing  tree  shrews,  the  tupaias  of  Africa  (Fig.  112),  in  many 
characters  resemble  the  hypothetic  ancestral  forms  of  Creta- 
ceous time  from  which  the  primates  (monkeys,  apes,  and  man) 
may  have  radiated. 


\ 


ORIGIN  OF  MAM]VL\LS 


237 


Following  Cuvier,  Owen,  and  Huxley  in  Europe,  a  period 
of  active  research  in  this  country  began  with  Leidy  in  the 
middle  of  the  nineteenth  century  and  was  continued  in  the 
arid  regions  of  the  West  by  Cope,  Marsh,  and  their  succes- 
sors with  such  energy  that  America  has  become  the  chief  cen- 
tre of  vertebrate  palaeontology.  When  we  connect  this  research 
with  the  older  and  the  more  recent  explorations  by  men  of  all 
countries  in  Europe,  Asia,  Africa,  Australia,  and  South  Amer- 
ica, we  are  enabled  to  reconstruct  the  great  tree  of  mammalian 
descent  (Fig.  114)  with  far  greater  fulness  and  accuracy  than 
that  of  the  reptiles,  amphibians,  or  fishes  (Pisces). 

The  connection  of  the  ancestral  mammals  wdth  a  reptilian 
t}T)e  of  Permian  time  is  theoretically  established  through  the 
survival  of  a  single  branch  of  primitive  egg-laying  mammals 
(Monotremata,  Fig.  113)  in  Australia  and  New  Guinea;  while 
the  whole  intermediate  division,  consisting  of  the  pouched 
mammals  (Marsupialia)  of  Australia,  w^hich  bring  forth  their 
young  in  a  very  immature  condition,  represents  on  the  great 
continent  of  Australia  an  adaptive  radiation  which  also  sprang 
from  a  small,  primitive,  tree-living  j  whales, 
type  of  mammal,  typified  by  the  ex- 
isting opossums  of  North  and  South 
America  (Fig.  113).  The  third  great 
group  (Placentalia)  includes  the 
mammals  in  which  the  unborn 
young  are  retained  a  longer  period 
within  the  mother  and  are  nourished 
through  the  circulation  of  nutrition 
in  the  placenta. 

The  adaptive  radiation  of  the  ten 
great  branches  of  the  placental  stock  from  the  primitive  insec- 
tivorous arboreal  ancestors  produced  a  mammalian  fauna  which 


2 .  Seals  (marine  carnivores) . 

3.  Carnivores  (terrestrial). 

4.  Insectivores. 

5.  Bats. 

6.  Primates: 

Lemurs, 
Monkeys, 
Apes, 
Man. 

7.  Hoofed  mammals. 

8.  Manatees. 

9.  Rodents. 
10.  Edentates. 


238 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


inhabited  the  entire  globe  until  the  comparatively  recent  period 
of  extermination  by  man,  who  through  the  invention  of  tools 
in  Middle  Pleistocene  time,  about  125,000  years  ago,  became 
the  destroyer  of  creation. 

Single  Character  Evolution  and  Physicochemical 

Correlation 

The  principal  modes  of  evolution  as  we  observe  them  among 
the  mammals  are  threefold,  namely: 

I.  The  modes  in  which  new  characters  first  appear,  whether 
suddenly  or  gradually  and  continuously,  whether  accidentally 
or  according  to  some  law. 

II.  The  modes  in  which  characters  change  in  proportion, 
quantitatively  or  intensively,  both  as  to  form  and  color. 

III.  The  modes  in  which  all  the  characters  of  an  organism 
respond  to  a  change  of  environment  and  of  individual  habit. 

The  key  to  the  understanding  of  these  three  modes  is  to  be 
sought  first  in  changes  of  food  and  in  changes  of  the  medium 
in  which  the  mammals  move,  whether  on  the  earth,  in  the 
water,  or  in  the  air.  The  complexity  of  the  environmental 
influence  becomes  like  that  of  a  lock  with  an  unlimited  number 
of  combinations,  because  the  adaptations  of  the  teeth  to  varied 
forms  of  insectivorous,  carnivorous,  and  herbivorous  diet  may 
be  similar  among  mammals  living  in  widely  different  habitat 
zones,  while  the  adaptations  of  the  locomotor  apparatus,  the 
limbs  and  feet,  to  the  primary  arboreal  zone  may  radiate 
into  structures  suited  to  any  one  of  the  remaining  ten  life 
zones.  Thus  there  is  invariably  a  double  adaptive  and  inde- 
pendent radiation  of  the  teeth  to  food  and  of  the  limbs  to  pro- 
gression, and  therefore  two  series  of  organs  are  evolving.  For 
example,  there  always  arises  a  more  or  less  close  analogy  be- 
tween the  teeth  of  all  insect-eating  mammals,  irrespective  of 


CHARACTER   EVOLUTION 


239 


the  habitat  in  which  they  find  their  food.  Similarly  there 
arises  a  more  or  less  close  analogy  between  the  motor  organs  of 
all  the  mammals  living  in  any  particular  habitat;  thus  the  glis- 
sant  or  volplaning  limbs  of  all  aero-arboreal  types  are  exter- 
nally similar,  irrespective  of  the  ancestral  orders  from  which 

HABITAT  CHANGE  ACCOMPANYING  CHANGE  OF  FUNCTION 

rLYINGI 


AERIAL 


PTEROSAUR* 


A£R2  ARBORt 


IVCXJ>L>NING» 


■  FLVING  •  PHALANOERS 
GALEOPITMECUS 
"FLYING    SQUIRRELS 


FLYING"  U2ARO 


ARBOREAL 


(LEAPING  OR 

CLIMBING  IN 

TREESl 


PHALANCERS.  LEMURS 

SQUIRRELS 

SLOTHS 


cham>C(leon8 


ICE  KANOANOC 


ARBORS  TERRt 


(TRANSITIONAL 
TO  TERRESTRIAU 


MACAQUES 
GORILLA 


TERRESTRIAL 


(WALKING 
RUNNING 
JUMPINGI 


MANY  INSECT'VORES 

BABOONS.  MANY  RUNNING  TYPES 

JUMPING  RODENTS       KANGAROOS 


TERRS  FOSSORt 


(TRANSITIONAL 
TO  OIGGINGI 


MANY  CLAWED  MAMMALS 


MANY  REPTILES 
'     TORTOISES 


FOSSORIAL 
TERRS  AQUATIC 


(OIOGINGI 


MOLES.  POUCHED  MOLES 


(TRANSITIONAL 
PARTIALLY  AQUATIO 


SHREWS    YAPOK.  BEAVER 
CAPYBARA.  HIPPOPOTAMUS, 
POLAR  BEARS.  OTTERS 


MANY  LIZARDS 

MANY  TURTLES 


AQUATIC.FLUVLE 
»»     LITTORAL 


(LIVING  IN  FRESH 
WATER) 


CROCODILES 
POND  TURTLES 


(LIVING  ALONG  SHORE 
OR  IN  ESTUARIES) 


SEA-OTTER 
MANATEE 
SEALS   WALRUS 


NOTHOSAURS 

MANY  EXTINCT  REPTILES 


PELAGIC 
ABYSSAL 


(EXCLUSIVELY 
MARINE) 


SEA  TURTLES 
ICHTKfYOSAURS 


(LIVING  AT  GREAT  DEPTHS 
OR  DIVING  TO  GREAT  DEPTHSI 


FINBACK  WHALES 


SOME  MOSASAURS 


MOTOR  ADAPTATIONS  OF  DIFFERENT  ANIMALS  TO  SIMILAR  LIFE  ZONES 

Fig.  115.     Adaptive  Radiation  of  the  Mammals. 

The  mammals,  probably  originating  in  arboreal  leaping  or  climbing  phases,  radiate 
adaptively  into  all  the  other  habitat  zones  and  thus  acquire  many  types  of  body  form 
and  of  locomotion  more  or  less  convergent  and  analogous  to  those  previously  evolved 
among  the  reptiles  (shown  in  the  right-hand  column),  the  amphibians,  and  the  fishes. 
Diagram  by  Osbom  and  Gregory. 

they  are  derived.  A  mammal  may  seek  any  one  of  twelve 
different  habitat  zones  in  search  of  the  same  general  kind  of 
food;  conversely,  a  mammal  living  in  a  single  habitat  zone 
may  seek  within  it  six  entirely  different  kinds  of  food. 

This  principle  of  the  independent  adaptation  of  each  organ 
of  the  body  to  its  own  particular  function  is  in  keeping  with 
the  heredity  law  of  individual  and  separate  evolution  of  ^^char- 
acters'* and  ** character  complexes''   (p.  147),  and  is  fatal  to 


240 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


some  of  the  hypotheses  regarding  animal  structure  and  evolu- 
tion which  have  been  entertained  since  the  first  analyses  of 
animal  form  were  made  by  Cuvier  at  the  beginning  of  the  last 
century.  The  independent  adaptation  of  each  character  group 
to  its  own  particular  function  proves  that  there  is  no  such  essen- 
tial correlation  between  the  structure  of  the  teeth  and  the  struc- 
ture of  the  feet  as  Cuvier  claimed  in  what  was  perhaps  his 
most  famous  generalization,  namely,  his  ''Law  of  Correlation.'' ^ 
Again  this  principle,  of  twofold,  threefold,  or  manifold  adap- 
tation, is  fatal  to  any  form  of  belief  in  an  internal  perfecting 
tendency  which  may  drive  animal  evolution  in  any  particular 
direction  or  directions.  Finally,  it  is  fatal  to  Darwin's  original 
natural-selection  hypothesis,  which  would  imply  that  the  teeth, 
limbs,  and  feet  are  varying  fortuitously  rather  than  evolving 
under  certain  definite  although  still  unknown  laws. 

The  adaptations  which  arise  in  the  search  of  many  varieties 
of  food  and  in  overcoming  the  mechanical  problems  of  loco- 
motion, offense,  and  defense  in  the  twelve  different  habitat 
zones  are  not  fortuitous.     On  the  contrary,  observations  on 
successive  members  of  families  of  mammals  in  process  either 
of  direct,  of  reversed,  or  of  alternate  adaptation  admit  of  but 
one  interpretation,  namely,  that  the  evolution  of  characters  is 
in  definite  directions  toward  adaptive  ends;  nor  is  this  definite 
direction  limited  by  the  ancestral  constitution  of  the  heredity- 
chromatin  as  conceived  in  the  logical  mind  of  Huxley.     The 
passage  m  which  Huxley  expressed  this  conception  is  as  follows : 
''The  importance  of  natural  selection  will  not  be  impaired 
even  if  further  inquiries  should  prove  that  variability  is  definite, 
and  is  determined  in  certain  directions  rather  than  in  others,  by 

1  Cuvier's  law  of  correlation  has  been  restated  by  Osbom.  There  is  a  fundamental 
correlation,  coordination,  and  cooperation  of  all  parts  of  the  organism,  but  not  of  the 
kind  conceived  by  Cuvier,  who  was  at  heart  a  special  creationist.  Contrary  to  Cuvier  s 
claim,  it  is  impossible  to  predict  from  the  structure  of  the  teeth  what  the  structure  of 
the  feet  may  prove  to  be. 


CHARACTER  EVOLUTION 


241 


conditions  inherent  in  that  which  varies.     It  is  quite  conceiv- 
able that  every  species  tends  to  produce  varieties  of  a  limited 
number  and  kind,  and  that  the  effect  of  natural  selection  is  to 
favor  the  development  of  some  of  these,  while  it  opposes  the 
development    of    others    along    their   predetermined    lines    of 
modification."^     It  is  true  that  the  variations  of  the  organ- 
ism are  in  some  respects  limited  in  the  heredity-chromatin,  as 
Huxley  imagined;  on  the  contrary,  every  part  of  a  mammal 
may  exhibit  such  plasticity  in  course  of  geologic  time  as  enables 
it  to  pass  from  one  habitat  zone  into  another,  and  from  that 
into  still  others  until  finally  traces  of  the  adaptations  to  pre- 
vious habitats  and  anatomical  phases  may  be  almost  if  not 
entirely   lost.     The  heredity-chromatin  never  determines   be- 
forehand into  what  new  environment  the  lot  of  a  mammal 
family  may  be  cast;  this  is  determined  by  cosmic  and  plane- 
tary changes  as  well  as  by  the  appetites  and  initiative  of  the 
organism  (p.  114).     For  example,  one  of  the  most  remarkable 
instances  which  have  been  discovered  is  that  of  the  reversed 
aquatic  adaptation  of  Zeuglodon,'^  first  terrestrial,  then  aquatic, 
in   succession   a   dog-like,   a    fish-like,  and  finally  an  eel-like 
mammal.     These  peculiar  whales  (Archaeoceti)  appear  to  have 
originated  in  the  littoral  and  pelagic  waters  of  Africa  in  Eocene 
time   from   a   purely   terrestrial   ancestral    form    of    mammal 
(allied  to  Hyccnodon),  in  which  the  body  is  proportioned  like 
that  of  the  wolf  or  dog,  and  this  terrestrial  mammal  in  turn 
was  descended  from  a  very  remote  arboreal  ancestor.     Thus 
in  its  long  history  the  Zeuglodon  passed  through  at  least  three 
habitat  zones  and  as  many  life  phases. 

Yet  in  another  sense   Huxley  was  right,  for   palaeontolo- 

^  Huxley,  Thomas,  1893,  p.  223  (first  published  in  1878). 

=  Zeuglodon  itself  is  a  highly  specialized  side  branch  of  the  primitive  toothed  whales. 
The  true  whales  may  have  arisen  from  the  genera  Protocetus,  probably  ancestral  to  the 
toothed  whales,  and  Patriocetus  which  combines  characters  of  the  zeuglodonts  and 
whalebone  whales. 


242 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


gists  actually  observe  in   the  characters  springing  from   the 
heredity-chromatin  a  predetermination  of  another  kind,  namely, 
the  origin  through  causes  we  do  not  understand  of  a  tendency 
toward  the  independent  appearance  or  birth  at  different  periods 
of  geologic  time  of  similar  new  and  useful  characters.     In  fact, 
a  very  large  number  of  characters  spring  not  from  the  visible 
ancestral  body  forms  but  from   invisible  predispositions  and 
tendencies  in  the  ancestral  heredity-chromatin.     For  example, 
all  the  radiating  descendants  of  a  group  of  hornless  mammals 
may  at  different  periods  of  geologic  time  give  rise  to  similar 
horny  outgrowths  upon  the  forehead.     This  heredity  principle 
partly  underlies  what  Osborn  has  termed  the  law  of  rectigra- 
dation.     Moreover,  once  a  new  character  or  group  of  characters 
makes  its  visible  appearance  in  the  body  its  invisible  chromatin 
evolution  may  assume  certain  definite  directions  and  become 
cumulative  in  successive  generations  in  accordance  with  the 
principle   of   Mutationsrichtung,    first   perceived    by  Neumayr 
(p.  138);  in  other  words,  the  tendency  of  a  character  to  evolve 
in  one  direction  often  accumulates  in  successive  generations 
until  it  reaches  an  extreme. 

The  application  of  our  law  of  quadruple  causes,  namely,  of 
the  incessant  action,  reaction,  and  interaction  of  the  four 
physicochemical  complexes  under  the  influence  of  natural 
selection,  to  the  definite  and  orderly  origin  of  myriads  of  char- 
acters such  as  are  involved  in  the  transformation  of  a  shrew 
type  of  mammal  into  the  quadrupedal  wolf  t>T>e  and  of  the 
wolf  t>'pe  into  the  Zeuglodon  eel  type,  has  not  yet  even  ap- 
proached the  dignity  of  a  working  hypothesis,  much  less  of  an 
explanation.  The  truth  is  that  the  causes  of  the  orderly  co- 
adaptation  of  separable  and  independent  characters  still  remain 
a  mystery  which  we  are  only  beginning  to  diml\'  penetrate. 
As  another  illustration  of  the  complexity  of  the  evolution 


CHARACTER   EVOLUTION 


243 


process  in  mammals,  let  us  observe  the  operation  of  DoUo's 
law  of  alternate  adaptation  (p.  202)  in  the  evolution  of  the  tree 
kangaroo  {Dendrolagus) ,  belonging  to  the  marsupial  or  pouched 
division  of  the  Mammalia.  This  is  a  case  where  many  of  the 
intermediate  stages  are  known  to  survive  in  existing  types. 
These  tree  kangaroos  theoretically  have  passed  through  four 
phases,  as  follows:  (i)  An  arboreo-terrestrial  phase,  including 
primitive  marsupials  like  the  opossum,  with  no  special  adap- 


AERIAL 


A^RS  ARBORt 
ARBOREAL 


FEET  OF  CLIMBING  TYPE.  GREAT  TOE  OPPOSABLE; 
i  FOURTH  TOE  ENLARGED 


TREE  KANGAROOS  WITH  FEET  OF 
LEAPING  TYPE.  BUT  READAPTED  FOR 

CLIMBING 


ARB0R5  TERRS' 
TERRESTRIAL 


\    PRIMITIVE  MARSUPIALS 

WITH  NO  SPECIAL  ADAPTATIONS  , 
FOR  CLIMBING 


^  KANGAROOS  WITH  FEET  OF  LEAPING  TYPE  |  J 
GREAT  TOE  REDUCED  OR  ABSENT                        V^ 
\  FOURTH  TOE  MUCH  ENLARGED | 


Fig.  116.    Four  Phases  of  Alterxatixg  .Vdaptation  in  the  Kangaroo  Marsupials, 

According  to  Dollo's  Law. 

1.  Primitive  arboreo-terrestrial  phase — tree  and  ground  living  forms. 

2.  Primitive  arboreal  phalanger  phase — tree-living  forms. 

3.  Kangaroos — terrestrial,  saltatorial  phase — ground-living,  jumping  forms. 

4.  Tree  kangaroos — secondarily  arboreal,  climbing  phase. 

tations  for  climbing;  (2)  a  true  arboreal  phase  of  primitive  tree 
phalangers  with  the  feet  specialized  for  climbing  purposes 
through  the  opposability  of  the  great  toe  (hallux),  the  fourth 
toe  enlarged;  (3)  a  cursorial  terrestrial  phase,  typified  by  the 
kangaroos,  with  feet  of  the  leaping  type,  the  big  toe  (hallux) 
reduced  or  absent,  the  fourth  toe  greatly  enlarged;  (4)  a  second 
arboreal  phase,  typified  by  the  tree  kangaroos  {Dendrolagus) , 
with  limbs  fundamentally  of  the  cursorial  terrestrial  leaping 
type  but  superficially  readapted  for  climbing  purposes.  It 
is  clear  that  there  can  be  no  internal  perfecting  tendency 
or  predetermination  of  the  heredity-chromatin  to  anticipate 
such  a  tortuous  course  of  evolution  from  terrestrial  into  arbo- 
real life,  from  arboreal  back  to  a  highly  specialized  terrestrial 


244  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

life,  and  finally  from  the  leaping  over  the  ground  of  the  kan- 
garoo into  the   incipiently   specialized   arboreal  phase  of   the 
tree  kangaroo.     In  the  evolution  of  the  tree  kangaroos  adap- 
tation is  certainly  not  limited  by  the  inherent  tendencies  of 
the  heredity-chromatin  to  evolve  in  certain  directions.     The 
physicochemical   theory  of   these  remarkable  alternate  adap- 
tations is  that  an  animal  leaving  the  terrestrial  habitat  and 
taking  on  arboreal  habits  initiates  an  entirely  new  series  of 
actions,  reactions,  and  interactions  with  its  physical  environ- 
ment, with  its  life  environment,  in  its  body  cell  and  individual 
development,  and,  in  some  manner  entirely  unknown  to  us,  in 
its  heredity-chromatin,  which  begins  to  show  new  or  modified 
determiners   of  bodily   character.     That   natural   selection   is 
continuously  operating  at  every  stage  of  the  transformation 

there  can  be  no  doubt. 

One  interpretation  which  has  been  offered  up  to  the  pres- 
ent time  of  the  mode  of  transformation  of  a  terrestrial  into  an 
arboreal  mammal  is  through  a  form  of  Darwinism  known  as 
the  ^^ organic  selection''  or  '^coincident  selection"  h>T3othesis, 
which  was  independently  proposed  by  Osborn,^  Baldwin,  and 
Lloyd  Morgan,  namely:  that  the  individual  bodily  modifications 
and  adaptations  caused  by  growth  and  habit  (while  not  them- 
selves heritable)  would  tend  to  preserve  the  organism  during  the 
long  transition  into  arboreal  life;  they  would  tend  to  nurse  the 
family  over  the  critical  period  and  allow  time  to  favor  all  pre- 
dispositions and  tendencies  in  the  heredity-chromatin  toward 
arboreal  function  and  structure,  and  would  tend  also  to  elim- 
inate all  structural  and  functional  predispositions  in  the  hered- 
ity-chromatin which  would  naturally  adapt  a  mammal  to  life 
in  any  one  of  the  other  habitat  zones.     This  interpretation  is 
consistent  with  our  law  that  selection  is  constantly  operating 

1  Osborn,  H.  F.,  1897. 


CAUSES  OF  EVOLUTION 


245 


( 


on  all  the  actions,  reactions,  and  interactions  of  the  body,  but 
it  does  not  help  to  explain  the  definite  origin  of  new  characters 
which  cannot  enter  into  ''organic  selection"  before  they  exist. 
Nor  is  there  any  evidence  that  while  adapting  itself  to  one 
mode  of  life  fortuitous  variations  in  the  heredity-chromatin  for 
every  other  mode  of  life  are  occurring. 

Theoretic  Causes  of  Evolution  in  Mammals 

We  have  thus  far  described  only  the  modes  of  evolution  and 
said  nothing  of  the  causes.  In  speculating  on  the  causes  of 
character  evolution  in  the  mammals,  in  comparison  with  similar 
body  forms  and  characters  in  the  lower  vertebrates  and  even 
in  the  invertebrates,  it  is  very  important  to  keep  in  mind  the 
preceding  evidence  that  mammalian  heredity-chromatin  may 
preserve  all  the  useful  functional  and  structural  properties  of 
action,  reaction,  and  interaction  which  have  accumulated  in 
the  long  series  of  ancestral  life  forms  from  the  protozoan  and 
even  the  bacterial  stage. 

Since  structurally  the  mammalian  embryo  passes  through 
primitive  protozoan  (single-celled)  and  metazoan  (many-celled) 
phases,  it  is  probable  that  chemically  it  passes  through  the 
same.  The  heredity-chromatin  even  in  the  development  of 
the  highest  mammals  still  recalls  primitive  stages  in  the  devel- 
opment of  the  fishes,  for  example,  the  gill-arch  structure  at 
the  side  of  the  throat,  which  through  change  of  function  serves 
to  form  the  primary  cartilaginous  jaws  (Meckelian  cartilages) 
of  mammals  as  well  as  the  bony  ossicles  which  are  connected 
with  the  auditory  function  of  the  middle  ear  (Reichert's 
theory).  Similarly  profound  structural  ancestral  phases  in 
protozoan,  fish,  and  reptile  structure  pervade  every  part  of  the 
mammalian  body.  In  race  evolution  there  may  be  changes  of 
adaptation  as  in  the  law  of  change  of  function  {Prinzip  des  Funk- 


246 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


CAUSES  OF   EVOLUTION 


247 


tionsu'echsels) J  first  clearly  enunciated  by  Anton  Dohrn  in  1875. 
But  no  function  is  lost  without  good  cause,  and  the  heredity- 
chromatin  retains  every  character  which  through  change  of 
function  and  adaptation  can  be  made  useful. 

The  same  law  which  we  observe  in  the  conservation  of  all 
adaptive  characters  and  functions  will  probably  be  discovered 
also  in  the  conservation  of  ancestral  physicochemical  actions, 
reactions,  and  interactions  of  the  organism  from  the  protozoan 
stages  onward.  The  primordial  chemical  messengers — enzymes 
or  organic  catalyzers,  hormones  and  chalones,  and  other  accele- 
rators, retarders,  and  balancers  of  organ  formation  (see  p.  72) — 
are  certainly  not  lost;  if  useful,  they  are  retained,  built  up,  and 
unceasingly  complicated  to  control  the  marvellous  coordina- 
tions and  correlations  of  the  various  organs  of  the  mammalian 
body.  The  principal  endocrine  (internal  secretory)  as  well  as 
duct  secretory  glands  established  in  the  fish  stage  of  evolution 
(p.  160),  through  which  they  can  be  partly  traced  back  even  to  the 
lancelet  stage  (chordate),  doubtless  had  their  beginnings  among 
the  ancestors  (protochordates)  of  the  vertebrated  animals,  which 
extend  back  into  Cambrian  and  pre-Cambrian  time.  Since 
these  chemical  messenger  functions  among  the  mammals  are 
enormously  ancient,  we  may  attribute  an  equal  antiquity  to  the 
powers  of  chemical  storage  and  entertain  the  idea  that  the 
chromatin  potentiality  of  storing  phosphate  and  carbonate  of 
lime  for  skeletal  and  defensive  armature  in  the  protozoan 
stage  of  50,000,000  years'  antiquity  ^.s  the  same  chromatin 
potentiality  which  builds  up  the  superb  internal  skeletal  struc- 
tures of  the  Mammalia  and  the  highly  varied  forms  of  offen- 
sive and  defensive  armature  either  of  the  calcium  compound 
or  the  chitinous  type. 

It  is,  moreover,  through  the  fundamental  similarity  of  the 
physicochemical  constitution  of  the  fishes,  amphibians,  reptiles, 


i 


1 


birds,  and  mammals  that  we  may  interpret  the  similarities  of 
form  evolution  and  understand  why,  the  other  three  causes 
being  similar,  mammals  repeat  so  many  of  the  habitat  form 
phases  in  adaptation  to  the  environments  previously  passed 
through  by  the  lower  orders  of  life.  Thus  advancing  struc- 
tural complexity  is  the  reflection  or  the  mirror  of  the  invisible 
physicochemical  complexity;  the  visible  structural  complexity 
of  a  great  animal  like  the  whale  (Fig.  234),  for  example,  is 
something  we  can  grasp  through  its  anatomy;  the  physico- 
chemical  complexity  of  the  whale  is  quite  inconceivable. 

In  research  relating  to  the  physicochemical  complexity  of 
the  mammals,  so  notably  stimulated  by  the  work  of  Ehrlich 
and  further  advanced  by  later  investigators,  there  are  perhaps 
few  studies  more  illuminating  than  those  of  Reichert  and 
Brown^  on  the  crystals  of  oxyhemoglobin,  the  red  coloring 
matter  of  the  mammalian  blood.  Their  research  proves  that 
every  species  of  mammal  has  its  highly  distinctive  specific 
and  generic  form  of  hemoglobin  crystals,  that  various  degrees 
of  kinship  and  specific  affinity  are  indicated  in  the  crystallog- 
raphy of  the  hemoglobin.  For  example,  varieties  of  the  dog 
family,  such  as  the  domestic  dog,  the  wolf,  the  Australian 
dingo,  the  red,  Arctic,  and  gray  fox,  are  all  distinguished  by 
only  slightly  differing  crystalline  forms  of  oxyhemoglobin.  The 
authors'  philosophic  conclusions  arising  from  this  research  are 

as  follows:^ 

''The  possibilities  of  an  inconceivable  number  of  constitu- 
tional differences  in  any  given  protein  are  instanced  in  the  fact 
that  the  serum-albumin  molecule  may,  as  has  been  estimated, 
have  as  many  as  1,000,000,000  stereoisomers.  If  we  assume 
that  serum-globulin,  myoalbumin,  and  other  of  the  highest  pro- 

>  Reichert,  E.  T.,  and  Brown,  A.  P.,  1909,  pp.  iii-iv. 

'  Certain  insertions  in  brackets  being  made  for  purposes  of  comparison  with  other 
portions  of  this  series  of  lectures. 


248 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


teins  may  have  a  similar  number,  and  that  the  simpler  proteins 
and  the  fats  and  carbohydrates  and  perhaps  other  complex 
organic  substances,  may  each  have  only  a  fraction  of  this 
number,  it  can  readily  be  conceived  how,  primarily  by  differ- 
ences in  chemical  constitution  of  vital  substances,  and  secon- 


f 

1 

1 

\ 

.  ^■■#^ 

:*? 

Fig.  117.    Evolution  of  Proportion.    Adaptation  in  Length  of  Neck. 

Short-necked  okapi  (left),  the  forest-living  giraffe  of  the  Congo,  which  browses  upon  the 
lower  branches  of  trees. 

Long-necked  giraffe  (right),  the  plains-living  t>pe  of  the  African  savannas,  which  browses 
on  the  higher  branches  of  trees.     After  Lang. 

darily  by  differences  in  chemical  composition,  there  might  be 
brought  about  all  of  those  differences  which  serve  to  charac- 
terize genera,  species,  and  individuals.  Furthermore,  since  the 
factors  which  give  rise  to  constitutional  changes  in  one  vital 
substance  would  probably  operate  at  the  same  time  to  cause 
related  changes  in  certain  others,  the  alterations  in  one  may 
logically  be  assumed  to  serve  as  a  common  index  to  all. 

^^In  accordance  with  the  foregoing  statement  it  can  readily 
be  understood  how  environment,  for  instance,  might  so  affect 


CAUSES  OF  EVOLUTION 


249 


the  individuaPs  metabolic  processes  as  to  give  rise  to  modifica- 
tions of  the  constitutions  of  certain  corresponding  proteins  and 
other  vital  molecules  which,  even  though  they  be  of  too  subtle 
a  character  for  the  chemist  to  detect  by  his  present  methods, 
may  nevertheless  be  sufficient  to  cause  not  only  physiological 
and  morphological  differentiations  in  the  individual,  but  also 


Fig    118.      ShORT-FiNGEREDNESS  (BrACHYDACTYLY)  and  LONG-FlNGEREDNESS  (DOLICHO- 

dactyly).    Congenital,  and  Due  to  Internal  Secretion. 
(Left )     Congenital  brachydactyly,  theoretically  due  either  to  a  sudden  alteration  in  the 

chromatin  or  to  a  congenital  defect  in  the  pituitary  gland.     After  Drinkwater. 
(Centre.)     Brachydactyly,  after  birth,  due  to  abnormally  excessive  secretions  of  the 

pituitary  gland.     After  Cushing. 
(Right.)     Dolichodactyly,  after  birth,  due  to  abnormally  insufficient  secretions  of  the 

pituitary  gland.     After  Cushing. 

become  manifested  physiologically  [functionally]  and  morpho- 
logically [structurally]  in  the  offspring.'' 

The  above  summary  adumbrates  the  lines  along  which  some 
of  the  chemical  interactions,  if  not  causes,  of  mammalian  ev- 
olution may  be  investigated  during  the  present  century. 

The  cause  of  different  bodily  proportions,  such  as  the  very 
long  neck  of  the  tree-top  browsing  giraffe,  is  one  of  the  classic 
problems  of  adaptation.  In  the  early  part  of  the  nineteenth 
century  Lamarck  (p.  143)  attributed  the  lengthening  of  the  neck 


250 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


to  the  inheritance  of  bodily  modifications  caused  by  the  neck- 
stretching  habit.  Darwin  attributed  the  lengthening  of  the 
neck  to  the  constant  selection  of  individuals  and  races  which 
were  born  with  the  longest  necks.  Danvin  was  probably  right. 
This  is  an  instance  where  length  or  shortness  of  neck  is  ob- 
viously a  selective  survival 


character  in  the  struggle  for 
existence,  because  it  directly 
affects  the  food  supply. 

But  there  are  many  other 
changes  of  proportion  in  mam- 
mals, which  are  not  known  to 
have  a  selective  survival  value. 
We  may  instance  in  man,  for 
example,  the  long  head-form 
(dolichocephaly)  and  the  broad 
head-form  (brachycephaly) ,  or 
the  long-fingered  form  (dolicho- 
dactyly)  and  the  short-fingered 
form  (brachydactyly),  which 
have  been  interpreted  as  con- 


FiG.  119.  Result  of  Removing  the 
Thyroid  and  Parathyroid  Glands. 

(Right.)  Normal  sheep  fourteen  months 
old. 

(Left.)  A  sheep  of  the  same  age  from 
which  the  thyroids  and  parathyroids 
were  removed  twelve  months  previ- 
ously. 

After  Sutherland  Simpson. 


genital  characters  appearing  at 
birth  and  tending  to  be  transmitted  to  offspring.  Brachy- 
dactyly may  be  transmitted  through  several  generations,  but 
until  recently  no  one  has  suggested  what  may  be  its  possible 
cause. 

It  has  now  been  found^  that  both  the  short-fingered  con- 
dition (brachydactyly)  and  the  slender-fingered  condition  may 
be  induced  during  the  lifetime  of  the  individual  in  a  previously 
healthy  and  normal  pair  of  hands  by  a  diseased  or  injured  con- 
dition of  the  pituitar>'  body  at  the  base  of  the  brain.     If  the 

^Gushing,  Harvey,  1911,  pp.  253,  256. 


MODES   OF   EVOLUTION 


251 


secretions  of  the  pituitary  are  abnormally  active  (hyperpitui- 
tarism) the  hand  becomes  broad  and  the  fingers  stumpy  (Fig. 
118,  B).  If  the  secretions  of  the  pituitary  are  abnormally  re- 
duced (hypopituitarism)  the  fingers  become  tapering  and  slender 
(Fig.  118,  C).  Thus  in  a  most  remarkable  manner  the  internal 
secretions  of  a  very  ancient 
ductless  gland,  attached  to  the 
brain  and  originating  in  the 
roof  of  the  mouth  in  our  most 
remote  fish-like  ancestors,  affect 
the  proportions  both  of  flesh 
and  bones  in  the  fingers,  as 
well  as  the  proportions  of  many 
other  parts  of  the  body. 

Whether  this  is  a  mere  co- 
incidence of  a  heredity-chro- 
matin  congenital  character 
with  a  mere  bodily  chemical 
messenger  character  it  would 
be  premature  to  say.  It  cer- 
tainly appears  that  chemical  in- 
teractions from  the  pituitar>^  body  control  the  normal  and  ab- 
normal development  of  proportions  in  distant  parts  of  the  body. 

Chief  Modes  of  Evolution  of  Mammalian   Characters 

What  we  have  gained  during  the  past  century  is  positive 
knowledge  of  the  chief  modes  of  evolution;  we  know  almost  the 
entire  history  of  the  transformation  of  many  different  kinds  of 

mammals. 

These  modes  as  distinguished  from  the  unknown  causes  are 
expressed  in  the  following  general  laws:  first,  the  law  of  con- 
tinuity; Natura  non  facit  saltum,  there  is  prevailing  continuity 


Fig.  120.    Result   of   Removing   the 
Pituitary  Body. 

(Right.)  Normal  dog  twelve  months 
old. 

(Left.)  A  dog  of  the  same  age  and  litter 
from  which  the  pituitary  body  was 
removed  at  the  age  of  two  months. 

After  Aschner. 


252 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


m 


in  the  changes  of  form  and  proportion  in  evolution  as  in 
growth.  Second,  the  law  of  recti  gradation,  under  which  many 
important  new  characters  appear  definitely  and  take  an  adap- 
tive direction  from  the  start;  third,  the  law  of  acceleration  and 
retardation^  witnessed  both  in  racial  and  individual  develop- 
ment, whereby  each  character  has  its  own  velocity,  or  rate  of 
development,  which  displays  itself  both  in  the  time  of  its  origin, 
in  its  rate  of  evolution,  and  its  rate  of  individual  development. 
This  last  law  underlies  the  profound  changes  of  proportion  in 
the  head  and  different  parts  of  the  body  and  limbs  which  are 
among  the  dominant  features  of  mammalian  evolution.  In 
the  skeleton  of  mammals  very  few  new  characters  originate; 
most  of  the  changes  are  in  the  loss  of  characters  and  in  the 
profound  changes  of  proportion.  For  example,  by  the  addi- 
tion of  many  teeth  and  by  stretching  or  pulling,  swelling  or 
contracting,  the  skeleton  of  a  tree  shrew  may  almost  be  trans- 
formed into  that  of  a  whale. 

The  above  laws  are  the  controlling  ones  and  make  up  four- 
fifths  of  mammalian  evolution  in  the  hard  parts  of  the  body. 
So  far  as  has  been  observed  the  remaining  fifth  or  even  a 
much  smaller  fraction  of  mammalian  evolution  is  attributable 
to  the  law  of  saltation,  or  discontinuity,  namely,  to  the  sudden 
appearance  of  new  characters  and  new  functions  in  the  hered- 
ity-chromatin.  For  example,  the  sudden  addition  of  a  new 
vertebra  or  vertebrae  to  the  backbone,  which  gives  rise  to  the 
varied  vertebral  formulae  in  different  orders  and  even  the  dif- 
ferent genera  of  mammals,  or  the  sudden  addition  of  a  new 
tooth  are  instances  of  saltatory  evolution  in  the  hard  parts 
of  the  body.  There  are  also  many  instances  of  the  sudden 
appearance  of  new  functional,  physiological,  or  physicochem- 
ical  characters,  such  as  immunity  or  non-immunity  to  certain 
diseases. 


> 


ADAPTATION  TO  ENVIRONMENT  253 

Responses  of  Mammal  Characters  to  Changing 

Environment 

Buffon  was  the  first  to  observe  the  direct  responses  of  mam- 
mals to  their  environment  and  naturally  supposed  that  en- 
vironment was  the  cause  of  animal  modification,  chiefly  in 
adaptation  to  changes  of  climate.  It  did  not  occur  to  him 
to  inquire  whether  these  modifications  were  heritable  or  not, 
any  more  than  it  did  to  Lamarck. 

It  is  now  generally  believed  that  these  reactions  are  for 
the  most  part  modifications  of  the  body  cells  and  body  chro- 
matin only,  which  give  rise  to  what  may  be  known  as  environ- 
mental species,  as  distinguished  from  true  chromatin  species 
which  are  founded  upon  new  or  altered  hereditary  characters. 
Of  the  former  order  are  many  geographic  varieties  and  doubtless 
many  geographic  species.  These  visible  species  of  body  cell 
characters  are  quite  distinct  from  the  invisible  species  of 
heredity-chromatin  characters.     Both  occur  in  nature. 

Geologic  and  secular  changes  of  environment  have  preceded 
many  of  the  most  profound  changes  in  the  evolution  of  the 
mammals,  which  interlock  and  counteract  with  their  physical 
and  life  environments  quite  as  closely  as  do  the  reptiles,  am- 
phibians, and  fishes;  yet  a  very  large  part  of  mammalian  evo- 
lution has  proceeded  and  is  proceeding  quite  independently  of 
change  of  environment.  Thus  environment  holds  its  rank  as 
one  of  the  four  complexes  of  the  causes  of  evolution  instead  of 
being  the  cause  par  excellence  as  it  was  regarded  in  the  brilUant 
speculations  of  Buffon. 

The  interlocking  of  mammals  with  their  life  environment  is 
extremely  close,  namely,  with  Bacteria,  Protozoa,  Insecta,  and 
many  other  kinds  of  Invertebrata,  with  other  Vertebrata,  as 
well  as  with  the  constantly  evolving  food  supply  of  the  plant 


254 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


m 


world;  consequently  the  vicissitudes  of  the  physical  environ- 
ment as  causes  of  the  vicissitudes  of  the  life  environment  of 
mammals  afiford  the  most  complex  examples  of  interlocking 
which  we  know  of  in  the  whole  animal  world.  In  other  words, 
the  mammals  interlock  in  relation  to  all  the  surviving  forms  of 
the  life  which  evolved  on  the  earth  before  them.  Although 
suggested  nearly  a  century  ago  by  Lyell,  the  demonstration  is 
comparatively  recent  that  one  of  the  principal  causes  of  the 
extinction  of  certain  highly  adaptive  groups  of  mammals  is 
their  non-immunity  to  the  infections  spread  by  Bacteria  and 
Protozoa.^  Thus  a  change  of  environment  and  of  climate  may 
not  afTect  a  mammal  directly  but  may  profoundly  affect  it  in- 
directly through  insect  life. 

These  closely  interlocking  relations  of  the  mammals  with 
their  physicochemical  environment  and  their  life  environment 
have  been  subject  to  constant  disturbances  through  the  geo- 
logic and  geographic  shifting  of  the  twelve  or  more  habitat 
zones  which  they  occupy.  Yet  the  earth  changes  during  the 
Tertiary,  the  era  during  which  mammalian  evolution  mainly 
took  place,  were  less  extreme  than  those  during  Mesozoic  and 
Palaeozoic  time.  This  is  because  the  trend  of  development  of 
the  earth's  surface  and  of  its  climate  during  the  past  3,000,000 
years  has  been  toward  continental  stability  and  lowering  of 
general  temperature  in  both  the  northern  and  southern  hemi- 
spheres, terminating  in  the  geologically  sudden  advent  of  the 
Glacial  Epoch,  with  its  alternating  periods  of  moisture  and 
aridity,  cold  and  heat,  which  exerted  the  most  profound  influ- 
ence upon  the  food  supply,  insect  barriers,  and  other  causes 
affecting  the  migrations  of  the  Mammalia.  These  causes  com- 
pletely change  the  general  aspect  of  the  mammalian  world  in 

^  For  the  history  and  discussion  of  this  entire  subject  see  Osbom,  H.  P.:  "The  Causes 
of  Extinction  of  Mammalia,"  Amcr.  Naturalist,  vol.  XL,  November  and  December, 
1906,  pp.  769-795,  829-859. 


ADAPTATION  TO   ENVIRONMENT 


255 


I 


the  whole  northern  hemisphere.  South  America,  and  Australia, 
and  leave  only  the  world  of  African  mammalian  life  untouched. 
The  water  content  of  the  atmosphere  during  the  3,000,000  years 
of  the  Age  of  Mammals  has  tended  toward  a  repetition  of  the 
environmental  conditions  of  Permian  and  Triassic  times  in 
the  development  of  areas  of  extreme  humidity  as  well  as  areas 
of  extreme  aridity,  interrupted,  however,  by  widespread  humid 
conditions  in  the  Pleistocene  Epoch.  Marine  invasion  of  the 
continents  of  Europe  and  North  America,  while  far  less  ex- 
treme than  during  Cretaceous  time,  has  served  to  give  us  the 
complete  history  of  the  littoral  and  marine  Mollusca,  both  in 
the  eastern  and  western  hemispheres,  which  is  the  chief  basis 
of  the  geologic  time  scale  as  discovered  in  the  Paris  basin  by 
Brogniart  at  the  beginning  of  the  eighteenth  century. 

The  clearest  conception  of  the  length  of  Tertiary  time  is 
afforded  (Fig.  121)  by  the  completion  in  Eocene  time  of  the 
Rocky  Mountain  uplift  of  America  and  the  eastern  Alps  of 
Europe,  by  the  elevation  of  the  Pyrenees  in  Oligocene  time, 
by  the  rise  of  the  wondrous  Swiss  Alps  between  the  Oligocene 
and  Miocene  Epochs,  and  finally  by  the  creation  of  the  titanic 
Himalaya  chain  in  the  latter  part  of  Miocene  time. 

Through  the  phenomena  of  the  migration  of  various  kinds 
of  mammals  from  continent  to  continent,  we  are  able  to  date 
with  some  precision  the  rise  and  fall  of  the  land  bridges  and 
the  alternating  periods  of  connection  and  separation  of  the 
two  northern  continental  masses,  Eurasia  and  America,  as  well 
as  of  the  northern  and  southern  continents.  Few  writers 
maintain  seriously  for  Tertiary  time  the  ^^ equatorial  theory"  of 
connection  between  the  eastern  and  western  hemispheres  such 
as  figures  largely  in  the  speculations  of  Suess,  Schuchert,  and 
others  in  relation  to  plant  and  animal  migrations  of  Palaeozoic 
and  Mesozoic  time.     The  less  radical  ''bipolar  theory"  that 


♦ 


2  56  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

the  eastern  and  western  hemispheres  were  connected  both  at 
the  north  pole  and  at  the  south  pole,  or  through  Arctic  and 
Antarctic  land  areas,  still  has  many  adherents,  especially  in 


PER 

GLACIAL        S  oy^'^E'^'**''^ "~*^^ 

I         PLIOCENE     SOOOV 
HIMALAYAS  ~^       ' 

SWISS  ALPS 
PYRENEES 


EASTERN  ALPS 
(Party) 


I     I  JURA^S\C 


+fm 


HTi 


i-O. 


am 


I  I  I  I  i  M  I  ,  ;  I 


I  1 


I     PE,RM1^»^ 

h  I  r,  1 1  r 
1 .  1 1 


+4W 


z 


DS 

•:'py^TERNA<»v '     A      GLACIAL 


o 

teJ 

2 


TTT 


ir' 


THE  HERCYNIAN  BELT  OF    ,..,  ,        ,  .         , 
CENTRAL  EUROPE  ?    /////  ^  /  ^  ''^ 


//  CARBONir,ERj)gS' ' 


I   '    '    '    M    !    I    I    '  I 


ROCKV 
MOUNTAIN 


AGE 

OF 

MAMMALS 


I    >   l'   i 
I    I    I       l]   I   I 
TRIASSIC     I  ■   I 
l"  I  "l   '      '  I  '  I  , 


SCOTTISH  HIGHLANDS/ 


SILURIAN 


FINLAND 

E. SCANDINAVIA 

S. BOHEMIA 


15000 


ORDOVICIAN 

17000 


CAMBRIAN 


16000 


ALOONKIAN 


ARCHAEAN 


IL«K»MIC.;,,„. 

SIERRA  NEVADA 

AGE 

PALISAOe 

OF 

REPTILES 

APPALACHIAN 

AND 

AMPHIBIANS 

ACADIAN 


TACONIC 


AGE 
OF 

FISHES 

AND 

INVERTEBRATES 


7  PRt-CAMBRIAN 


?  ARCHAEAN 


CERTAIN  MOUNTAIN 
REVOLUTIONS  OF 
EUROPE  AND  ASIA 


CHIEF  MOUNTAIN 
REVOLUTIONS  OF 
NORTH  AMERICA 


Fig.  121.    Main  Subdivisions  of  Geologic  Time. 
The  subdivisions  are  not  to  the  same  scale.    The  notches  at  the  sides  of  the  scale  (which 
is  simplified  from  that  on  p.  153)  represent  chiefly  the  periods  of  mountam  uplift  m  the 
northern  hemisphere  of  the  Old  World  (left)  and  of  the  New  World  (right). 

regard  to  the  former  relations  of  the  Australian  continent 
and  South  America  through  the  now  partly  sunken  continent 
of  Antarctica.     The    still    more    conservative    ''north    polar 


ADAPTATION  TO  ENVIRONMENT 


257 


DISTRIBUTION   OF  PRIMATE 

^^       MoDCMM    ANTMROWiOfA-vioHHEV 

I  '-''/  ^  'v 

LCHU«»I^A  (L£HaM,LMI&,TMUcO 

C(   E0C(NC(anD  0ii6OCtMt>i.CMUII0iDS 


theory''  of  Wallace,  of  an  exclusively  northern  land  connection 
of  the  eastern  and  western  hemispheres  during  Tertiary  time, 
has  recently  been  maintained  by  Matthew^  as  adequate  to 
explain  all  the  chief  facts  of  mammalian  migration  and  geo- 
graphic evolution. 

The   feet   and   the   teeth   of   mammals  become   so   closely 
adapted  to  the  medium  in  which  they  move  and  the  kind  of 

food    consumed    that __„ 

through    the  interpreta-         — ..„..,....  _^  <         1 

tion  of  their  structure 
we  shall  in  time  write  a 


fairly  complete  physio- 
graphic and  climatic  his- 
tory of  the  Tertiary 
Epoch  along  the  lines  of 
the  investigations  in- 
itiated by  Gaudry  and 
Kowalevsky.  Through 
the  successive  adapta- 
tions of  the  limbs  and 
sole  of  the  foot  and  the 
adaptations  of  the  teeth, 
which  are  most  delicately 
adjusted — the  former  to  impact  with  varying  soils  and  the 
latter  to  the  requirements  of  the  consumption  of  various  forms 
of  nourishment — we  may  definitely  trace  the  influences  or 
rather  the  adaptive  responses  to  the  habitat  subzones,  such  as 
the  forest,  forest-border,  meadow,  meadow-border,  river-border, 
the  lowland,  the  upland,  the  meadow-fertile,  the  meadow-arid, 
the  plains,  and  the  desert-arid.  This  mirror  of  past  geography, 
climate,  evolution  of  plant  life  in  the  anatomy  of  the  Kmbs 

1  Matthew,  W.  D.,  1915. 


Fig.  122.    The  North  Polar  Theory  of  the 
Distribution  of  Mammals. 

A  zenith  view  of  the  earth  from  the  north  pole, 
showing  (arrows)  the  North  Polar  theory  of  the 
geographic  migrations  and  distribution  of  the 
mammals,  especially  of  the  Primates  (monkeys, 
lemurs,  and  apes).     After  W.  D.  Matthew,  1915. 


258 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


and  feet,  is  one  of  the  most  fascinating  fields  of  philosophic 

study. 

In  the  more  humid,  semi-forested  regions,  which  preserve 
the  physiographic  conditions  of  early  Eocene  times  (Fig.  123), 
we  discover  most  of  the  examples  of  the  survival  of  primitive 
mammalian  forms  and  functions.  The  borderland  between 
the  extremes  of  aridity  and  humidity  has  afforded  the  most 


Fig.  123.    Scene  in  Western  Wyoming  in  Middle  Eocene  Time. 
The  period  of  the  four-toed  mountain  horse,  Orohippiis  (right),  of  the  Uintathere  (left), 
and  of  the  Titanothere  (left  lower) .     From  study  for  a  mural  decorat ion  in  the  American 
Museum  of  Natural  History  by  Charies  R.  Knight  under  the  author's  direction. 

favorable  habitats  for  the  rapid  evolution  of  all  the  forms  of 
terrestrial  life.  From  these  favored  regions  the  mammals 
have  entered  the  semi-arid  and  arid  deserts,  in  which  also 
evolution  has  been  relatively  rapid.  Since  Tertiary  geologic 
succession  is  nearly  unbroken  we  can  now  trace  the  evolution 
of  many  families  of  the  carnivores,  the  greater  number  of  the 
hoofed  mammals,  and  the  rodents,  with  few  interruptions 
through  the  entire  3,000,000  years  of  Tertiary  time.  It  is 
through  our  very  close  observation  of  the  origin  and  history 
of  numerous  single  characters  as  exhibited  in  pala^ontologic 
lines  of  evolution  that  the  three  chief  modes  (p.  251)  of  mam- 


GEOGRAPHIC   DISTRIBUTION 


259 


malian  evolution  and  the  continued  definite  direction  and  dif- 
ferences of  velocity  in  the  development  of  characters  have 
been  discovered. 

General  Succession  of  Mammalian  Life  in  North 

America 

In  Upper  Cretaceous  and  Palaeocene  time  we  find  that  the 
northern  hemisphere  is  covered  with  an  archaic  adaptive  radi- 
ation of  mammals  distinguished 
by  the  extremely  small  size  of 
the  brain  and  clumsy  mechanics 
of  the  skeleton.  Of  these  the 
carnivorous  forms  radiate  into  a 
number  of  families  adapted  to  a 
great  variety  of  feeding  and  lo- 
comotor habits  which  are  anal- 
ogous to  the  families  of  existing 
Carnivora.   Similarly  the  hoofed 


r 

1 

^T 

9Hi|:'<^^^^^ 

m 

'■■  i 

?*•. 

^■^ 

^1 

wm 

Fig.  124.    Two  Stages  in  the  Early 
Evolution  of  the  Ungulates. 

Pantolambda  {A),  an  archaic  Palaeocene 
form  which  transforms  into  Coryphodon 
(B),  a  Lower  Eocene  form  of  increased 
size,  with  greatly  enlarged  head,  ab- 
breviated tail,  and  defensive  tusks. 
This  transformation  occupied  a  period 
estimated  at  500,000  years,  nearly  one- 
sixth  of  Tertiary  time.  Restorations 
in  the  American  Museum  of  Natural 
History,  by  Osborn  and  Knight. 


mammals  (Condylarthra,  Am- 
blypoda)  divide  into  swift- 
footed  (cursorial)  and  heavy- 
footed  (graviportal)  forms,  the 
latter  including  the  Amblypoda 
{Coryphodon  and  Dinoceras). 
From  surviving  members  of  this 
archaic  adaptive  radiation  of  small-brained  mammals  there  arise 
all  the  stem  forms  of  the  orders  existing  to-day,  which  almost 
without  exception  have  now  been  traced  back  to  the  close  of 
Eocene  time,  namely,  the  ancestors  of  the  whales,  of  the  modern 
families  of  carnivores,  insectivores,  bats,  lemurs,  rodents,  and 
the  edentates  (armadillos  and  ant-eaters).  Especially  remark- 
able is  the  discovery  in  the  Lower  Eocene  of  the  ancestors  of 


26o 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


the  modern  horses,  tapirs,  rhinoceroses,  and  various  types  of 
cloven-footed  animals. 

A  very  general  principle  of  mammalian  evolution  is  illus- 
trated in  Fig.  124  (A,  B),  namely,  the  increase  of  size  character- 
istic of  all  the  herbivorous  mammals,  which  almost  without 
exception  are  in  the  beginning  extremely  small  forms  that 
evolve  into  massive  forms  possessing  for  defense  either  power- 


1 


»k.» 


Fig.  125.    A  Primitive  Whale  from  the  Eocene  of  Alabama. 

Zeuglodoti  cctoides  exhibits  a  secondary  elongate,  eel-shaped  body  form  analogous  to  that 
of  many  of  the  aquatic,  free-swimming,  surface-dwelling  reptiles,  aquatic  amphibians, 
and  fusiform  fishes.  Restoration  by  Gidley  and  Knight  in  the  American  Museum  of 
Natural  History. 

ful  tusks  or  horns.  The  most  conspicuous  example  of  very 
rapid  evolution  which  has  taken  place  prior  to  the  close  of 
Eocene  time  is  that  of  the  great  primitive  whale  Zeuglodon 
cetoides,  discovered  in  the  Upper  Eocen^e  of  Alabama,  and  now 
known  to  have  been  distributed  eastward  to  the  region  of  the 
Mediterranean.  As  described  above  (p.  241),  as  an  example  of 
reversed  adaptation  and  evolution,  this  animal  had  already 
passed  through  a  prior  terrestrial  phase  and  had  reached  a 
stage  of  extreme  specialization  for  marine  life.  These  zeu- 
glodonts  parallel  several  of  the  marine  groups  of  reptiles  (Figs. 
76,  87),  also  certain  of  the  amphibians  and  fishes  (Figs.  60,  44), 


GEOGRAPHIC   DISTRIBUTION 


261 


in  the  extreme  elongation  and  eel-like  mode  of  propulsion  of 

the  body. 

A  zoogeographic  feature  of  Eocene  life  is  the  strong  and  in- 
creasing evidence  of  migration  between  South  America  and 
North  America  by  means  of  land  connection  in  late  Cretaceous 
or  basal  Eocene  time,  between  the  northern  and  southern 
hemispheres,  which  was  then  interrupted  for  1,000,000  or  per- 
haps 1,500,000  years  until  the  middle  of  the  Pliocene  Epoch, 
when  the  South  American  t>pes  again  appear  in  North  Amer- 
ica. Another  relation  which  has  been  established  by  recent 
discoveries  is  seen  in  the  resemblance  between  certain  Rocky 
Mountain  primates  (lemurs)  and  those  existing  at  the  present 
time  in  the  Malayan  Peninsula. 

North  America  and  western  Europe  pass  alike  through 
three  great  phases  of  mammalian  life  in  Eocene  time:  first,  the 
archaic  phase  of  the  Palaeocene;  second,  a  long  phase  in  which 
the  archaic  and  modern  mammals  of  the  Lower  Eocene  inter- 
mingle; third,  a  very  prolonged  period  from  the  Lower  to  the 
Upper  Eocene,  in  which  Europe  and  North  America  are  widely 
separated  and  each  of  the  ancestral  types  of  mammals  undergoes 
an  independent  evolution.  This  is  followed  in  Oligocene  time 
by  a  phase  in  which  the  animal  Hfe  of  western  Europe  and 
North  America  was  reunited.  Again  in  Miocene  time  a  fur- 
ther wave  of  European  mammalian  life  sweeps  over  North 
America,  including  the  advance  wave  of  the  great  order  Pro- 
boscidea  embracing  both  mastodons  and  elephants  which  ap- 
pear to  have  originated  in  Africa  or  in  southern  Asia.  During 
the  entire  Miocene  and  Pliocene  Epochs  there  is  more  or  less 
unity  of  evolution  between  North  America,  Europe,  and  Asia, 
but  it  is  a  very  striking  fact  that  in  Middle  PHocene  time, 
when  a  wave  of  South  American  life  enters  North  America, 
certain  very  highly  characteristic  forms  of  North  American 


262 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


mammals  (camels)  enter  Europe.  In  late  Pliocene  and  early 
Pleistocene  time  the  grandest  epoch  of  mammalian  life  is 
reached;  certain  great  orders  like  the  proboscidians  and  the 
horses,  with  very  high  powers  of  adaptation  as  well  as  of  migra- 
tion, spread  over  every  continent  except  Australia. 


Fig.  126.    North  America  in  Upper  Oligocene  Time. 

East  of  the  recently  bom  Rocky  Mountains  the  region  of  the  Great  Plains  was  made  up 
of  broad  fluviatile  flood-plains,  fan-deltas,  and  lagoons,  accumulating  the  detritus  of  the 
Rocky  Mountains  on  the  west  and  with  a  general  eastern  drainage.  It  was  the  scene 
of  a  continuous  evolution  of  a  plains  fauna  of  mammals  for  a  period  of  1,500,000  years. 
Detail  from  the  globe  model  in  the  American  Museum  by  Chester  A.  Reeds  and  George 
Robertson,  after  Schuchert. 

This  great  epoch  of  mammalian  distribution  is  followed  by 
the  Pleistocene  phases  in  the  northern  and  southern  hemi- 
spheres, at  the  close  of  which  the  world  wears  a  greatly  im- 
poverished aspect;  the  northern  hemisphere  banishes  all  the 
forms  of  mammalian  life  evolving  in  the  southern  hemisphere 


' 


CHANGES  OF  PROPORTION 


263 


and  in  the  tropics,  and  the  high  table-lands  of  Africa  alone 
retain  the  grandeur  of  the  Pliocene  Epoch. 

The  Definite  Course  of  Chromatin   Evolution  in 

THE  Origin  of  New  Characters  Partly 

Predetermined  by  Ancestry 

Some  of  the  most  universal  laws  as  to  the  modes  (p.  251)  of 
evolution  emerge  from  the  comparative  study  of  the  horses. 


Fig.  127.  Two  Stages  in  the  Evolution  of  the  Titanotheres. 
Transformation  of  the  small  hoofed  quadruped  Eotilanops  {A)  of  the  Eocene— a  relatively 
light-limbed,  swift-moving,  cursorial  herbivore— into  the  gigantic  Brontothcriiim  (B)  of 
the  Lower  Oligocene — a  ponderous,  slow-moving,  graviportal  type,  horned  for  offense 
and  defense.  These  titanotheres  were  remotely  related  to  the  existing  rhinoceroses, 
horses,  and  tapirs,  but  they  became  suddenly  extinct  on  attaining  this  impressive 
stage  of  evolution.  They  exemplify  the  increase  of  size  characteristic  of  the  evolution 
of  the  greater  number  of  the  hoofed  Herbivora.  The  time  during  which  this  trans- 
formation occurred  is  estimated  at  1,200,000  years— about  one-third  of  the  whole 
Tertiary  Epoch. 

the  proboscidians,  and  the  rhinoceroses,  from  areas  so  widely 
separated  geographically  that  there  was  no  possibility  of  hy- 
bridizing or  of  a  mingling  of  strains.  For  example,  during  a 
period  estimated  at  not  less  than  500,000  years  the  horses  of 
France,  Switzerland,  and  North  America  evolve  in  these  widely 


264 


THE   ORIGIN  AND    EVOLUTION  OF  LIFE 


separated  regions  in  a  closely  similar  manner  and  develop 
closely  similar  characteristics  in  approximately  a  similar  length 
of  time.     The  same  is  true  of  the  widely  separated  lines  of 

descendants  from  the  mas- 
todons, elephants,  and  rhi- 
noceroses.    This  law  of 
uniform  evolution  and  of 
the   development   inde- 
pendently in  descendants 
from  the  same  ancestors  of 
closely   similar  characters 
is   confirmed   in   Osborn's 
study  of  the  evolution  of 
the  titanotheres  (Fig.  127). 
In    these    animals,   which 
have  been  traced  through 
discoveries  of   their  fossil 
remains  over  a  period  of 
time   extending   from   the 
beginning   of    the   Lower 
Eocene   to   the  beginning 
of  the   Middle  Oligocene, 
inclusive,    is    exhibited    a 
nearly  continuous,^    un- 
broken transformation 
from  the  diminutive  Eoti- 
tanops  of  the  Lower  Eocene 
to  the  massive  Brontothe- 
Hum  of  the  Lower  Oligocene,  the  latter  form  being  so  far  as 
known  the  most  imposing  product  of  mammalian  evolution, 

iThe  continuity  is  broken  by  the  extinction  of  one  branch  and  the  survival  of  an- 
other. It  is  a  continuity  of  character  rather  than  of  lines  of  descent.  In  some  cases 
there  is  a  continuity  both  of  characters  and  of  branches. 


Fig.  128.    Stages  in  the  Evolution  of  the 
Horn  in  the  Titanotheres. 

This  shows  that  these  important  weapons  arise 
as  rectigradations,  i.  e.,  orthogenetically  and 
not  as  the  result  of  the  selection  of  chance  or 
fortuitous  variations.  Horns,  large,  4,  Bron- 
totherium  platyceras,  Lower  Oligocene;  horns, 
small,  3,  Protitanothcrium  cmarginatiim,  Upper 
Eocene;  horns,  rudimentary,  2,  Manteoceras 
mankoceras,  Middle  Eocene;  hornless  stage, 
I,  Eotitanops  borealis,  Lower  Eocene. 

Models  in  the  American  Museum  of  Natural 
History,  prepared  for  the  author  by  Erwin  S. 
Christman. 


CHANGES  OF  PROPORTION 


265 


with  the  exception  of  the  Proboscidea.  Every  known  step  in 
this  transformation  is  determinate  and  definite,  every  additional 
character  which  has  been  observed  arises  according  to  a  fixed 
law  and  not  according  to  any  principle  of  chance.  In  the 
eleven  principal  branches  which  radiate  from  the  earliest  known 
forms  {Eotitanops  gregoryi)  of  this  family  exactly  similar  new 
characters  arise  quite  independently  at  different  periods  of 
geologic  time  which  are  separated  by  the  lapse  of  tens  of  thou- 
sands of  years. 

The  titanotheres  exhibit  an  absolutely  independent  but 
definite  origin  and  development  in  each  branch;  so  far  as  ob- 
served, every  new  character  has  its  own  rate  of  evolution 
and  its  own  peculiar  kind  of  form  change;  for  example,  in  cer- 
tain branches  of  the  family  the  horns  will  appear  many  thou- 
sands of  years  later  in  the  evolution  history  than  in  other 
branches,  and  after  their  appearance  in  many  instances  they 
may  exhibit  a  singular  inertia,  or  lack  of  momentum,  over  a 
long  period  of  time,  which  is  exactly  in  accord  with  our  gen- 
eral principle  (p.  149)  that  every  character  has  its  own  rate 
of  velocity  both  in  individual  development  and  in  racial  de- 
velopment. 

The  Origin  of  New  Proportional  Characters  Not 

Predetermined  by  Ancestry 

The  titanotheres  exhibit  another  very  important  principle, 
namely,  that  the  linear  proportions  of  the  bones  of  the  limbs 
are  exactly  adapted  to  the  weight  they  are  destined  to  carry 
and  to  the  speed  which  they  are  destined  to  develop;  in  other 
words,  the  speed  and  the  weight  of  all  these  great  herbivora 
may  be  very  precisely  estimated  by  ratios  and  indices  of  the 
proportionate  lengths  of  the  different  segments  of  the  limbs, 
upper,   middle,   and   lower.     These  proportionate  lengths  are 


266 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


not  predetermined  by  the  heredity-chromatin,  because  the 
same  law  of  limb  proportion  prevails  in  all  heavy,  slow-mov- 
ing mammals,  whatever  their  descent;  for  example,  this  law 
holds  among  the  heavy,  slow-moving  reptiles,  the  Sauropoda 
(Fig.  97),  as  well  as  among  the  heavy,  slow-moving  mammals. 
The  most  beautiful  adjustment  of  the  proportions  of  the 
limb  segments  to  speed  is  observed  in  the  evolution  of  the 

horses  (Fig.  130).  Here  we  see 
that  the  upper  segments  (hu- 
merus, femur)  are  abbreviated, 
while  the  lower  segments  (fore- 
arm, lower  leg,  manus,  and  pes) 
are  elongated.  This  is  precisely 
the  reverse  of  the  conditions 
obtaining  among  the  slow-mov- 
ing titanotheres  and  proboscid- 
ians (Fig.  131).  Among  the 
horses,  too,  the  same  law  pre- 
vails and  governs  the  very 
precise  adjustment  of  the  ratios 
of  each  of  the  limb  segments, 
quite  irrespective  of  ancestry. 
In  the  swift  Ilipparion  of  Amer- 
ica, for  example,  the  highest 
phase  of  equine  adaptation  to 
speed,  the  indices  and  ratios  of  the  limb  segments  are  very 
similar  to  those  in  the  existing  prong-horn  antelopes  {Antiloca- 
pra)  of  our  western  plains.  Contemporary  with  the  Hipparion 
of  Pliocene  time,  adapted  to  racing  over  hard,  stony  ground, 
is  the  relatively  slow-moving,  forest-living  horse  {Hypohippiis) 
of  the  river  borders  of  western  North  America  (Fig.  130),  in 
which  the  limb  proportions  are  quite  different.     There  is  reason 


Fig.  129.    Horses  of  Oligocene  Time. 

The  horses  frequenting  the  semi-arid 
plains  of  Oligocene  times  present  an 
intermediate  stage  in  the  evoUition  of 
of  cursorial  motion — Mcsohippus,  with 
a  narrow,  three- toed  type  of  foot, 
elongate,  graceful  limbs,  and  teeth  with 
crowns  beginning  to  be  adapted  to  the 
comminution  of  silicious  grasses  in 
accommodation  to  the  contemporane- 
ous world-wide  evolution  of  grassy 
plains.  This  law  of  the  contemporane- 
ous evolution  of  an  environment  of 
grassy  plains  and  of  swift-moving 
Herbivora  was  first  clearly  enunciated 
by  Kowalevsky  in  1873. 

Restorations  by  Osborn,  painted  by 
Charles  R.  Knight,  in  the  American 
^luseum  of  Natural  History. 


B 


B^ 

— J  ..  « 

_^'  **  f  ( 

!  H  t    i  »  «  i  {      ma  CI 

(      e  !  '  t  C  £  1  «  1 

Fig.  130.    Stages  in  the  Evolution  of  the  Horse. 

(Left.)  An  ascending  scries  of  Oligocene  three-toed  horses  (/I,  B,  C),  showing  their  evolu- 
tion in  size,  form,  and  dental  structure,  which  involved  continuous  change  in  thousands 
of  distinct  characters  and  occupied  a  period  of  time  estimated  at  100,000  to  200,000  years. 

(Right.)  Two  Upper  Miocene  American  types  of  horses,  Ilipparion  (F),  with  limbs  pro- 
portioned like  those  of  the  deer,  representing  the  climax  of  the  swift-moving,  grassy 
plains  type,  in  contrast  with  Ilypohippiis  {D,  £),  a  conservative  forest  and  browsing 
type.  This  is  an  instance  of  the  survival  of  an  ancient  browsing  type  in  an  ancient 
forested  environment  (D,  £),  while  in  the  adjacent  grassy  plains  there  exists  contem- 
poraneously the  fleet  Ilipparion  (F). 

Skeletons  mounted  in  the  American  Museum  of  Natural  History.  Restoration  under 
the  direction  of  the  author,  painted  by  Charles  R.  Knight. 

267 


268 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


to  believe  that  this  animal,  like  the  existing  okapi,  was  protected 
by  coloration  and  by  its  swamp-living  habits. 

The  above  examples  illustrate  the  general  fact  that  changes 
of  proportion  make  up  the  larger  part  of  mammalian  evolution 
and  adaptation.     The  gain  and  loss  of  parts,  the  presence  and 
absence  of  parts,  which  is  so  conspicuous  a  phenomenon  in 
heredity  as  studied  from  the  Mendelian  standpoint,  is  a  com- 
paratively rare  phenomenon.     These  changes  of  proportion  are 
brought  about  through  the  greater  or  less  velocity  of  single 
characters  and  of  groups  of  characters;  for  example,  the  trans- 
formation of   the  four-toed  horse  of   the  base  of   the  Lower 
Eocene^  into  the  three-toed  embryo  of  the  modern  horse  is 
brought  about  by  the  acceleration  of  the  central  digit  and  the 
retardation  of  the  side  digits.     This  process  is  so  gradual  that 
it  required  1,000,000  years  to  accomplish  the  reduction  of  the 
fifth  digit,  which  left  the  originally  tetradactyl  horse  in  the 
tridactyl  stage  (Fig.  130);    and  it  has  required  2,000,000  years 
more  to  complete  the  retardation  of  the  second  and  fourth 
digits,  which  are  still  retained  in  the  chromatin  and  develop 
side  by  side  with  the  third  digit  for  many  months  during  the 
early  intrauterine  life  of  the  horse. 

No  form  of  sudden  change  of  character  (saltation,  muta- 
tion of  de  Vries)  or  of  the  chance  theory  of  evolution  (pp.  7,  8) 
accounts  for  such  precise  steps  in  mechanical  adjustment;  be- 
cause for  all  proportional  changes,  which  make  up  ninety-five  per 
cent  of  mammalian  evolution,  we  must  seek  a  similar  cause, 
namely,  the  cause  of  acceleration,  balance  or  persistence,  and 
retardation.  This  cause  may  prove  to  be  in  the  nature  of  phys- 
icochemical  interactions  (p.  71)  regulated  by  selection.  The 
great  importance  of  selection  in  the  evolution  of  proportion  is 

iThe  earliest-known  fossil  horses  are  four-toed,  having  lost  the  first  digit  (thumb). 
No  five-toed  fossil  horse  has  yet  been  found. 


CHANGES  OF  PROPORTION 


269 


demonstrated  by  the  universal  law  that  the  limb  proportions 
of  mammals  are  closely  adjusted  to  provide  for  escape  from 
enemies  at  each  stage  of  development. 

Africa  as  a  Great  Theatre  of  Radiation 

The  part  which  Africa  has  played  in  the  early  stages  of 
mammalian  evolution  is  a  matter  of  comparatively  recent  dis- 
covery,  and    we    are    not    yet 
positive  whether  the  great  life 
centre  of  North  Africa  was  not 
closely  related  to  that  of  south- 
ern Asia  in  Eocene  and  early 
Oligocene  time,  as  the  most  re- 
cent discoveries  appear  to  indi- 
cate.    At  all  stages  of  geologic 
history  Africa  was,  as  it  is  to- 
day, a  great  theatre  of  evolu- 
tion of  terrestrial  Hfe.     Accord- 
ing to  present  knowledge,  North 
Africa  developed  a  highly  varied 
fauna,  including  three  chief  ele- 
ments:   first,   types  which   are 
closely  ancestral  to  the  higher 
monkeys  and  apes,  and  which 
may  thus  be  related  to  man  him- 
self;   second,  a  series  of  forms 
which  attained  gigantic  size  and 
never  migrated  from  the  con- 
tinent  of   Africa,    but   became 
extinct;  and,  thirdly,  a  series  of  forms,  such  as  the  zeuglodons, 
ancestral   whales,    sirenians,    manatees,    and    dugongs,    which 
emerged  from  this  African  home  and  enjoyed  a  very  wide  dis- 


FiG.  131.    Epitome  of  Proportion  Evo- 
lution IN  THE  PrOBOSCIDEA. 

These  animals  originated  in  the  Palao- 
mastodon  (lower),  frequenting  the  an- 
cient borders  of  the  Nile  in  Egypt  dur- 
ing Oligocene  time,  which  developed 
during  a  period  of  1,500,000  years  into 
the  existing  types  of  the  Indian  and 
African  elephants  and  into  the  ancient 
type  of  the  Elephas  (upper). 

Restoration  in  the  American  Museum  of 
Natural  History  under  the  direction  of 
the  author,  painted  by  Charles  R. 
Knight. 


I 

/ 


270 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


tribution  in  the  northern  hemisphere  and  in  the  equatorial 

regions. 

Among  the  giant  tribes  which  issued  from  this  ancient  con- 
tinent the  evolution  of  the  proboscidians  gives  us  an  instance 
of  the  most  extreme  divergence  of  a  terrestrial  type  from  a 
related  family,  the  sirenians,  which  evolve  into  the  aquatic, 

fluviatile,  and  littoral  type  of 
the  existing  sea-cows  and  man- 
atees. 

In    the    transformation    of 
PalcEomastodon  (Fig.   131)  into 
Elephas   there   are   notable 
changes  of  proportion  as  well 
as  the  loss  of  many  characters, 
as  seen  in  the  disappearance  of 
the  lower   tusks,   the  enlarge- 
ment and  curvature  of  the  up- 
per tusks,  the  elongation  of  the 
proboscis,  the  abbreviation  of 
the  skull,  the  elongation  of  the 
limbs,  the  relative  abbreviation 
of  the  vertebrae  of  the  neck  and  of  the  backbone,  the  reduction 
of  the  tail.     The  limbs  become  of  the  weight-bearing  type,  the 
hind  limbs  attaining  proportions  which  converge  toward  those 
of  the  titano there  Brontotherium  (Fig.  127).    The  final  numerical 
loss  of  characters  as  witnessed  in  the  very  gradual  reduction  of 
the  lower  tusks  affords  an  instance  of  the  leisurely  methods  of 
nature,  for  the  process  requires  2,000,000  years  in  the  elephant 
line  while  in  the  mastodon  line  the  lower  tusks  were  still  pres- 
ent at  the  time  of  the  comparatively  recent  extinction  of  this 
animal,   which   occurred   since   the   final  glaciation   of   North 
America.     The  loss  of  parts  through  retardation  is  also  seen 


Fig.  132.     The  Ice-Fields  of  the 
Fourth  Glaciation. 

Southward  extension  of  the  ice-fields 
over  the  northeastern  United  States 
during  the  period  of  the  fourth  glacia- 
tion. After  studies  of  Chamberlain. 
Modelled  by  Howell. 


CHANGES  OF  PROPORTION 


271 


in  the  reduction  of  the  number  of  the  pairs  of  grinding  teeth, 
from  seven  to  six  and  finally  in  the  adult  modern  elephant 
stage  to  one.  The  addition  of  new  characters  is  principally 
observed  in  the  remarkable  evolution  of  the  plates  of  the  grind- 
ing teeth  and  of  the  elaborate  muscular  system  of  the  pro- 
boscis. It  is  very  important  to  note  that,  as  in  the  evolution 
of  the  horses  (p.  263),  this  evolution  independently  follows  sim- 
ilar lines  among  the  Proboscidea  throughout  all  parts  of  the 
world.  In  other  words,  the  unity  of  the  evolution  of  the 
proboscidians  in   various  parts  of  the   world  was  not  main- 


FiG.  133.    Grolt>s  of  Reindeer  {Rangifcr  tarandiis)  and  Woolly  Mammoth  {Elephas 

primigcnius). 

Conditions  of  the  reindeer-mammoth  period  of  Europe  during  the  maximum  cold  of  the 
fourth  glaciation  of  the  Glacial  Epoch.  Mural  painting  in  the  American  Museum  of 
Natural  History,  painted  by  Charles  R.  Knight,  under  the  direction  of  the  author. 

tained  by  interbreeding,  but  by  the  unity  of  ancestral  heredity 
and  the  unity  of  the  actions,  reactions,  and  interactions  of 
the  animals  with  their  environment.  Widely  separated  de- 
scendants of  similar  ancestors  may  evolve  in  a  closely  but  not 
entirely  similar  manner.  The  resemblances  are  due  to  the 
independent  gain  of  similar  new  characters  and  loss  of  old 
characters.  The  differences  are  chiefly  due  to  the  unequal  ve- 
locity of  characters;  in  some  lines  certain  characters  appear  or 
disappear  more  rapidly  than  others. 

The  general  fact  that  the  slow-breeding  elephants  evolved 
very  much  more  rapidly  than  the  frequently  breeding  rodents, 
such  as  the  mice  and  rats  (Murida^),  is  one  of  the  many  evi- 
dences that  the  rate  of  evolution  may  not  be  governed  by  the 
frequency  of  natural  selection  and  elimination.     For  example, 


272  THE  ORIGIN  AND  EVOLUTION  OF  LIFE 

in  the  murine  family  of  rodents,  the  annual  progeny  is  very 
numerous  and  reproduction  is  very  frequent,  while  among  the 
elephants  there  is  only  a  single  offspring  and  reproduction  is 
comparatively  infrequent,  yet  the  grinding  teeth  of  the  Pro- 
boscidea  evolve  far  more  rapidly  and  into  much  more  highly 
compHcated  structures  than  the  grinding  teeth  of  any  of  the 


Fig.  134.    Pleistocene  or  Glacial  Environment  of  the  Woolly  Rhinoceros. 
Rhinoceros  tichorhinus,  of  northern  Europe,  a  contemi)orary  of  the  woolly  mammoth. 
Restoration  in  the  American  Museum  of  Natural  History,  painted  by  Charles  R. 
Knight,  under  the  direction  of  the  author. 

rapidly  breeding  rodents.     If  evolution  were  due  to  the  natural 
selection  of  chance  variations  this  would  not  be  the  case. 

The  elephants,  like  the  horses,  afford  an  example  of  superb 
mechanical  perfection  in  a  single  organ,  the  teeth,  evolved  in 
relatively  slow-breeding  forms,  within  a  relatively  short  period 
of  geologic  time.  In  their  grinding-tooth  structure  the  Probos- 
cidea  closely  interlock  with  their  environment,  that  is,  there 
are  complete  transitions  of  dental  structure  between  partly 
grazing,  partly  browsing,  and  exclusively  browsing  forms,  such 


CHANGES  OF  PROPORTION 


273 


as  the  mastodon.  The  psychic  and  bodily  adaptability  and 
plasticity  of  the  Proboscidea  to  extreme  ranges  of  habitat  is 
paralleled  only  by  the  human  adaptation  to  extremes  of  climate 
which  is  achieved  through  the  intelligence  of  man.     The  woolly 


Fig.  135.    Pygmies  of  the  Hills  Compared  with  the  Plainsmen  of  West  Central 

New  Guinea. 

From  Rawling's  Lattd  of  the  New  Guinea  Pigmies,  by  permission  of  Seeley,  Service  & 
Co. — The  question  arises  whether  the  dwarfing  is  due  to  natural  selection,  to  prolonged 
unfavorable  environment,  or  to  abnormal  internal  secretions  of  certain  glands  like  the 
thyroid.  It  will  be  observed  that  the  dwarfing  is  disproportional,  the  heads  being 
relatively  large.     Compare  the  dwarfed  sheep  and  dog  in  Figs.  119  and  120. 

mammoth  (Fig.  131)  presents  one  extreme  of  proboscidian 
adaptation,  comparable  to  the  Eskimo  among  human  races  as 
superbly  adapted  to  the  rigors  of  the  arctic  climate,  while  the 
hairless  African  and  Indian  elephants  are  comparable  to  the 
hairless  human  races  living  under  the  equator. 


274 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


Undoubtedly  the  most  promising  field  for  future  palaeon- 
tological  research  and  discovery  is  in  Asia.  The  links  in  the 
series  of  mammals — especially  in  the  line  known  as  the  Pri- 
mates leading  into  the  ancestors  of  man,  namely,  the  Lemurs, 
Monkeys,  and  Apes— are  probably  destined  to  be  found  in 
this  still  very  imperfectly  explored  continent,  for  it  is  indicated 
by  much  evidence  that  the  still  unexplored  region  of  northern 
Asia  was  a  great  centre  of  animal  population  and  of  adaptive 
radiation  into  Europe  on  the  west  and  into  North  America 
on  the  northeast.  Ancient  vertebrate  fossils  from  this  vast 
region  are  as  yet  absolutely  unknown,  but  will  doubtless  be 
discovered,  and  it  is  here  that  the  Eocene,  and  perhaps  the 
Oligocene  ancestors  of  man  are  likely  to  be  unearthed,  that 
is,  in  deposits  of  the  first  half  of  the  Tertiary  Period.  Fos- 
sil records  of  the  descent  of  man  during  the  second  half  of 
the  Tertiary  also,  namely,  from  the  Oligocene  Epoch  to  the 
close  of  the  Pliocene  time,  we  beHeve  may  be  discovered  in 
Asia,  most  probably  in  the  region  lying  south  of  the  Flima- 

layas. 

This  subject  of  prehuman  ancestry  and  evolution  is  re- 
served for  the  concluding  series  of  Hale  Lectures,  but  in  our 
search  for  suggestions  as  to  the  causes  of  evolution,  especially 
along  the  lines  of  internal  physicochemical  factors  and  the 
doctrine  of  energy,  man  himself  is  proving  to  be  one  of  the 
most  helpful  of  all  mammals  because  chemically,  physically, 
and  experimentally  man  is  the  best  known  of  all  organisms  at 
the  present  time. 


I 


RETROSPECT  AND   PROSPECT 


Retrospect  and  Prospect 


275 


The  initial  question  raised  in  this  volume  arises  as  soon 
as  we  undertake  a  summary  of  evolution  as  we  see  it  in  the 
retrospect  of  the  ages. 

Does  the  energy  conception  of  evolution  bring  us  nearer 
to  the  causes  either  of  the  origin  or  of  the  transformation  of 
characters?  Before  answering  these  crucial  questions  let  us 
see  what  our  brief  survey  has  taught  us  as  to  the  kind  of  causes 
to  look  for. 

The  foregoing  comparison  in  the  second  part  of  this  vol- 
ume of  the  evolutionary  development  that  has  taken  place 
in  many  series  of  animals  belonging  to  the  five  great  classes 
of  vertebrates — fishes,  reptiles,  amphibians,  birds,  and  mam- 
mals— in  response  to  twelve  different  kinds  of  environment, 
gives  repeated  evidence  of  their  continuous  powers  of  ever- 
plastic  adaptation,  not  only  to  one  kind  of  physical  and 
life  environment,  but  to  any  direct,  reversed,  or  alternating 
change  of  environment  which  a  group  of  animals  may  en- 
counter either  on  its  own  initiative  or  by  force  of  circum- 
stances. 

In  the  large  vertebrates  we  are  enabled  to  observe  and 
often  to  follow  in  minute  details  this  continuous  adaptation 
not  merely  in  one,  but  in  hundreds  and  sometimes  in  thou- 
sands of  characters.  In  this  respect  a  vertebrate  differs  from 
a  relatively  simple  plant  organism  Hke  the  pea  or  the  bean 
on  which  some  of  the  prevaiUng  conceptions  of  evolution  have 
been  grounded.  In  the  well-ordered  evolution  of  these  single 
characters  we  have  a  picture  like  that  of  a  vast  army  of  sol- 
diers; the  organism  as  a  whole  is  Hke  the  army;  the  '^char- 
acters'' are  like  the  individual  soldiers;  and  the  evolution  of 
each  character  is  coordinated  with  that  of  every  other  char- 


I 


■'  i 


276  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

acter.  Sometimes  a  character  lags  behind  and  through  failure 
to  keep  pace  produces  the  dystelcogy  or  imperfect  fitness  of 
certain  parts  of  the  organism  observed  by  Metchnikoff  in  the 

human  body. 

Sometimes  there  are  serial  regiments  of  such  well-ordered 
characters  which  are  exactly  or  closely  aUke— for  example, 
the  1092  teeth  in  the  upper  jaw  of  the  iguanodont  dinosaur, 
Trachodon,  all  very  similar  in  appearance,  all  evolving  and  all 
perfectly  coordinated  in  form  and  function  with  the  910  teeth 
in  the  lower  jaw  of  the  same  animal.  There  are  other  serial 
regiments  of  characters,  however,  like  the  vertebrae  in  the 
backbone  of  a  large  dinosaur,  for  example,  in  which  every 
single  character,  large  and  smaU,  is  different  in  form  from 
every  other.  These  are  among  the  many  miracles  of  adapta- 
tion referred  to  in  the  Preface. 

The  evidence  for  this  continuous  and  more  or  less  adaptive 
direction  in  the  simultaneous  evolution   of  numberless    char- 
acters which  can  be  observed  only  by  means  of  an  ancestral 
fossil   series   was   unknown    to  the   master   mind   of    Darwin 
during  the  preparation  of  his  '^Origin  of   Species''   through 
his  observations  on  the  variations  of   domestic  animals  and 
plants  between  1845  and  1858;    for  it  was  not  until  the  dis- 
covery by  Waagen,  in  1869,  of  a  continuous  series  of  fossil 
ammonites,   in   which   minute   changes   originate  and  can  be 
followed  continuously,  that  the  rudiments  of  a  true  concep- 
tion of  the  orderly  and  continuous  modes  of  evolution  which 
prevail  in   nature  were  reached.     Among   invertebrates    and 
vertebrates,  this  conception  has  been   abundantly   confirmed 
by    modern    paleontology  in  all  its  branches,  namely,   that 
of  a  well-ordered  continuity  as  the  prevaihng  mode  of  evolu- 
tion.    This  is  the  greatest  contribution  which  palaeontology 
has  made  to  biology  and  to  natural  philosophy. 


RETROSPECT  AND   PROSPECT 


277 


Discontinuity  is  found  chiefly  in  those  characters  in  which 
a  continuous  mode  of  change  is  impossible.  As  to  the  physico- 
chemical  constitution  of  animals  and  plants  it  has  been  well 
said  that  there  can  be  no  continuity  between  two  distinct 
chemical  formulae,  or  in  many  physicochemical  functions  and 
reactions.  There  are  also  certain  form  and  proportion  char- 
acters in  which  continuity  is  impossible — for  example,  the 
sudden  addition  of  a  new  tooth  to  the  jaw,  or  of  a  new  verte- 
bra to  the  backbone. 

From  these  well-ascertained  facts  of  the  sudden  or  salta- 
tory appearance  of  characters,  some  have  rashly  inferred 
that  there  can  be  no  continuity  between  species,  whereas  it 
is  now  known  in  mammalogy,  in  palaeontology,  and  to  a  less 
extent  in  ornithology  that  a  large  number  of  so-called  species 
in  nature  show  a  complete  continuity.  Although  the  part 
which  sudden  changes  or  ''saltations"  from  character  to  char- 
acter play  in  experimental  evolution  and  artificial  selection 
is  very  prominent,  it  remains  to  be  seen  how  large  a  part  they 
play  under  natural  conditions. 

We  realize  that  it  is  far  more  difficult  to  ascertain  the  causes 
of  such  continuous  independent  and  more  or  less  orderly  and 
adaptive  evolution  of  single  characters  than  to  comprehend 
evolution  as  Darwin's  adherents  of  the  present  day  imagine  it 
to  be,  namely  fortuitous  and  saltatory,  for  it  is  incumbent  upon 
us  to  discover  the  cause  of  the  orderly  origin  of  every  single 
character.  The  nature  of  such  a  law  we  cannot  even  dream 
of  at  present,  for  the  causes  of  the  majority  of  vertebrate  adap- 
tations remain  wholly  unknown. 

Negatively  we  may  say  from  palaeontology  that  there  is 
positive  disproof  of  the  existence  of  an  internal  perfecting 
principle  or  entelechy  of  any  kind  which  would  impel  animals 
to  evolve  in  a  given  direction  regardless  of  the  direct,  reversed, 


I 


278 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


or  alternating  directions  taken  by  the  organism  in  seeking  its 
life  environment  or  physical  environment. 

It  is  true,  we  have  found  (p.  264)  among  the  descendants 
of  similar,  though  remote,  ancestors  something  determinate  or 
definite — a  similarity  which  reminds  us  of  the  potential  of  the 
physicist — as  to  the  origin  of  certain  characters  rather  than 
others  in  the  heredity-chromatin.  It  is  as  if  certain  latent 
power  or  potency  of  character-origin  in  the  chromatin  were 
there  waiting  to  be  called  forth.  It  is  partly  due  to  this, 
as  well  as  to  inheritance  of  a  similar  ancestral  form,  that  the 
mammals,  as  studied  by  the  comparative  anatomist,  are  so 
much  alike,  despite  their  superficial  differences  as  seen  by  the 
student  of  adaptation.  This  definite  or  determinate  origin 
of  certain  new  characters  appears  to  be  partly  a  matter  of 
hereditary  predisposition.  That  is,  animals  from  a  common 
stock  independently  give  rise  at  different  times  to  similar  new 
characters,  as  seen,  for  example,  in  the  origin  of  similar  horn 
defenses  and  similar  bony  and  dental  structures. 

The  conclusive  evidence  against  an  clan  vital  or  internal 
perfecting  tendency,  however,  is  that  these  characters  do 
not  spring  up  autonomously  at  any  time;  they  may  lie  dor- 
mant or  remain  rudimentary  for  great  periods  of  time,  and 
here  we  find  a  correspondence  which  may  be  only  an  analogy 
with  the  principle  of  latent  energy  in  physics.  They  require 
something    to    call  them  forth,  to   make   them  active,  so  to 

speak. 

It  is  in  this  function  of  arousing  such  character  predis- 
positions that  the  chemical  messenger  phenomena  of  inter- 
action in  the  organism  present  some  analogy  to  latent  energy, 
although  future  experiment  may  prove  that  this  does  not  con- 
stitute a  real  cause  or  likeness.  If  the  transformation  of  energy 
is  accelerated  in  certain  organs  or  parts  of  existing  organs  by  the 


\ 


H 


RETROSPECT  AND   PROSPECT 


279 


arrival  of  interacting  chemical  messengers  and  these  parts 
thereby  change  their  form  and  proportions,  it  is  not  incon- 
ceivable that  chemical  messengers  may  arouse  a  latent  new 
character  by  stimulating  the  transformation  of  energy  at  a 

specific  point. 

Then  character-velocity  must  be  considered.  Although 
we  may  find  that  in  the  course  of  evolution  in  one  group  of 
animals  a  character  moves  extremely  slowly,  it  lags  along, 
it  is  retarded,  as  if  partly  suffering  from  inertia,  or  perhaps, 
for  a  while  it  stops  altogether;  yet  in  another  group  we  may 
find  that  the  very  same  character  is  full  of  life  and  velocity, 
it  is  accelerated  like  the  alert  soldier  in  the  regiment.  Here 
again  is  a  point  where  the  energy  conception  of  evolution  may 
throw  a  gleam  of  light.  Some  of  the  phenomena  of  interaction 
in  the  organism  give  us  the  first  insight  into  the  possible  causes 
of  the  slow  or  rapid  movement  of  character  evolution — of  its 
acceleration  and  retardation.  Such  individual  character  move- 
ments may  govern  the  proportions  of  certain  parts  as  well 
as  of  all  parts  of  the  organism. 

Combined,  these  character  velocities  and  movements  create 
all  the  extraordinary  differences  of  proportion  which  dis- 
tinguish the  mammals— for  example,  the  extraordinarily  long 
neck  of  the  giraffe,  the  short  neck  of  the  elephant,  the  elongated 
skull  of  the  ant-eater,  the  abbreviated  head  of  the  tree  sloth. 
Wherever  such  changes  of  proportion  weigh  in  the  struggle 
for  existence  they  may  be  hastened  or  retarded  by  natural 

selection. 

We  discover  that  the  chief  principles  of  comparative 
anatomy  formulated  by  Aristotle,  Cuvier,  Lamarck,  Goethe, 
St.  Hilaire,  Dohrn,  and  other  philosophic  anatomists^  may 
all  be  expressed  anew  in  terms  treating  the  organism  as  a 

*  Russell,  E.  S.,  1916. 


li 


1 


28o 


THE  ORIGIN  AND   EVOLUTION  OF  LIFE 


complex  of  energies.  This  is  shown  in  a  final  scheme  of 
action,  reaction,  and  interaction^  which  is  an  elaboration  of  the 
simplified  scheme  expressed  on  page  i6  of  the  Introduction,  as 
follows: 

Coordinated  Activity  of  the  Organism  Within  Itself 


ACTION 

AND 

REACTION 

oj  certain  parts 

Chemical  synthesis 
proteins,  fats, 
carbohydrates 

Heat  and  Motion 

Nutrition,  digestion 

Respiration 
oxidation,  etc. 

Secretion 

Circulation 

Muscular   and   Skeletal 
system,  etc. 
organs  of  locomotion 

Reproductive  system: 
ovary  and  testis  tis- 
sues surrounding 
heredity-germ  cells 

All  other  phenomena 
under  the  laws  of 
Transformation,  Stor- 
age, and  Release  of 
Energy. 


INTERACTION 


-s— >- 


Physicochcmical  Agents 

Catalyzers 

enzymes 
Internal  secretions 

hormones  (accelerators), 

chalones  (retarders), 
Nervous  system 

accelerators,  retarders, 

inhibitors 

Functions  of  Organs 

Balance,  Equilibrium 

arrested  development 
Acceleration 

growth,  development 
Retardation 

atrophy,  degeneration 
Correlation 
Compensation 

reciprocal  atrophy 

and  hypertrophy 


ACTION 

AND 

REACTION 

oJ  other  parts 

Chemical  synthesis 
proteins,  fats, 
carbohydrates 

Heat  and  Motion 

Nutrition,  digestion 

Respiration 
oxidation,  etc. 

Secretion 

Circulation 

Muscular  and  Skeletal 
system,  etc. 
organs  of  locomotion 

Reproductive  system: 
ovary  and  testis  tis- 
sues surrounding 
heredity-germ  cells 

All  other  phenomena 
under  the  laws  of 
Transformation,  Stor- 
age, and  Release  of 
Energy. 


The  eternal  question  remains,  How  do  these  energy  phe- 
nomena which  govern  the  life,  form,  and  function  of  the  organ- 
ism interact  with  the  supposed  latent  and  potential  energy 
phenomena  of  the  heredity-germ  cells?  As  stated  in  the  Pref- 
ace and  Introduction,  this  question  can  only  be  answered  by 
experiment.     There  is  no  proof  at  present. 

1  This  notion  of  coordinated  activity  is  particularly  well  expressed  in  Mathews's 
Physiological  Chemistry  (1916),  a  volume  which  came  to  the  author  after  this  work  was 
written  (see  Appendix,  Notes  V  and  VI). 


CONCLUSION 


Conclusion 


281 


In  the  foregoing  pages  we  have  attempted  to  sketch  in 
broad  outlines  the  course  of  the  origin  and  evolution  of  Hfe 
upon  the  earth  in  the  light  of  our  present  imperfect  knowl- 
edge, which  offers  few  certainties  to  guide  us  and  probabiUties 
and  possibilities  innumerable  among  which  to  choose. 

The  difference  between  the  non-living  world  and  the  living 
world  seems  like  a  vast  chasm  w^hen  we  think  of  a  very  high 
organism  like  man,  the  result  of  perhaps  a  hundred  million 
years  of  evolution.  But  the  difference  between  primordial 
earth,  water,  and  atmosphere  and  the  lowliest  known  organisms 
which  secure  their  energy  directly  from  simple  chemical  com- 
pounds is  not  so  vast  a  chasm  that  we  need  despair  of  bridging 
it  some  day  by  solving  at  least  one  problem  as  to  the  actual 
nature  of  life— namely,  whether  it  is  solely  physicochcmical  in 
its  energies,  or  whether  it  includes  a  plus  energy  or  element 
which  may  have  distinguished  Life  from  the  beginning. 

The  energy  conception  of  the  origin  and  evolution  of  life, 
on  which  are  based  our  fresh  stimulus  to  experiment  and  re- 
newed hope  of  progress  in  solving  the  riddle  of  Heredity,  is 
as  yet  in  its  infancy.  Our  vision  will  doubtless  be  amplified 
by  experiment.  In  seeking  the  causes  of  the  complex  adapta- 
tions even  of  the  simplest  organisms  described  in  Chapters 
III  and  IV  we  soon  face  the  boundaries  of  the  unknown, 
boundaries  w^hich  human  imagination  entirely  fails  to  pene- 
trate, for  Nature  never  operates  as  man  expects  her  to,  and  we 
beHeve  that  imagination  itself  is  strictly  limited  to  recombina- 
tions of  ideas  which  have  come  through  observation. 

It  may  be  said  that  the  bulk  of  experimental  work  hitherto 
has  been  in  the  domain  of  action  and  reaction— here  lie  all  the 
simple  energy  processes  of  growth,  of  waste  and  repair,  of  use 


282 


THE  ORIGIN  AND  EVOLUTION  OF  LIFE 


and  disuse,  of  circulatory,  muscular,  digestive,  and  nervous 
action.  Lamarckism  has  sought  in  vain  for  evidences  of  the 
inheritance  of  the  effects  of  such  action  and  reaction  processes. 

Experiment  and  observation  in  the  mysterious  field  of  in- 
teraction are  relatively  new,  yet  they  are  now  being  pressed 
with  intensity  by  many  workers.  There  is  an  encouraging 
likeness — pointed  out  in  many  parts  of  this  volume — between 
some  of  the  effects  visibly  produced  in  the  body  by  internal 
secretions  and  other  chemical  messengers,  and  certain  of  the 
familiar  processes  of  germ  evolution,  especially  in  adaptation 
through  changes  of  proportion  (see  p.  268)  of  various  parts  of 
the  body — a  kind  of  adaptation  which  is  of  great  importance 
in  all  animals.  And  while  this  likeness  between  interaction 
and  germ  evolution  may  be  mere  coincidence  and  have  no 
deeper  significance,  it  is  also  possible  that  it  may  betoken 
some  real  similarity  of  cause. 

For  our  theory  of  action,  reaction,  and  interaction — which 
is  fully  set  forth  and  illustrated  in  the  second  and  third  chap- 
ters of  this  work,  dealing  with  biochemical  evolution  and  the 
evolution  of  bacteria  and  algae,  as  well  as  in  certain  sections 
of  the  chapters  describing  the  evolution  of  the  vertebrates — 
it  may  be  claimed  that  it  brings  us  somewhat  nearer  a  consis- 
tent physicochemical  conception  of  the  original  processes  of 
life.  If  our  theory  is  still  far  from  offering  any  conception  of 
the  nature  of  Heredity  and  the  causes  of  elaborate  Adaptation 
in  the  higher  organisms,  it  may  yet  serve  the  desired  purpose 
of  directing  our  imagination,  our  experiment,  and  our  observa- 
tion along  lines  whereby  we  may  attain  small  but  real  advances 
into  the  unknown.  i\s  pointed  out  in  our  Preface  and  Intro- 
duction the  only  processes  in  inorganic  Nature  and  in  living 
organisms  themselves  which  are  in  the  least  suggestive  of  the 
processes  of  Heredity  are  some  of  the  processes  of  interaction. 


CONCLUSION 


283 


We  know,  for  example,  that  certain  cells  of  the  reproduc- 
tive glands^  have  a  profound  and  commanding  influence  on 
all  the  body  cells,  including  even  the  brain-cell  centres  of 
thought  and  intelligence — all  this  is,  in  a  sense,  an  outflowing 
from  the  heredity-germ  region,  a  centrifugal  interaction.  Is 
there  any  reversal  of  this  process,  any  inflowing  or  centripetal  in- 
teraction whereby  chemical  messengers  from  any  part  of  the 
body  specifically  affect  the  heredity-germ,  and  thus  the  new  or- 
ganism to  which  it  will  give  rise?  This  is  one  of  the  first 
things  to  be  ascertained  by  future  experiment. 

Being  still  at  the  very  beginning  of  the  problem  of  the 
causes  of  germ  evolution — a  problem  which  has  aroused  curi- 
osity and  bafBed  inquiry  throughout  the  ages — it  were  idle  to 
entertain  or  present  any  settled  conviction  in  regard  to  it, 
yet  we  cannot  avoid  expressing  as  our  present  opinion  that 
these  causes  are  internal-external  rather  than  purely  internal — 
in  other  words,  that  some  kind  of  relation  exists  between  the 
actions,  reactions,  and  interactions  of  the  germ,  of  the  organ- 
ism, and  of  the  environment.  Moreover,  this  opinion  is  prob- 
ably capable  of  experimental  proof  or  disproof. 

We  may  well  conclude  with  the  dictum  of  Francis  Bacon,^ 
one  of  the  first  natural  philosophers  to  counsel  experiment, 
who  in  his  Novum  Organum  (1620)  shows  that  living  objects 
are  well  adapted  to  experimental  work,  and  points  out  that  it 
is  possible  for  man  to  produce  variations  experimentally: 

"  They  [i.  e.,  the  deviations  or  mutations  of  Na- 
ture] differ  again  from  singular  instances,  by  being 
much  more  apt  for  practice  and  the  operative  branch. 
For  it  would  be  very  difficult  to  generate  new  species, 
but  less  so  to  vary  known  species,  and  thus  produce 

•  Gcxxlale,  H.  D.,  1916;  Lillie,  Frank  R.,  191 7. 
=»  Bacon,  Francis,  1620,  book  II,  sec.  29,  p.  180. 


284  THE  ORIGIN  AND   EVOLUTION  OF  LIFE 

many  rare  and  unusual  results.  The  passage  from 
the  miracles  of  nature  to  those  of  art  is  easy ;  for  if 
nature  be  once  seized  in  her  variations,  and  the  caiise 
be  manifest,  it  will  be  easy  to  lead  her  by  art  to  such 
deviation  as  she  was  at  first  led  to  by  chance;  and 
not  only  to  that  but  others,  since  deviations  on  the 
one  side  lead  and  open  the  way  to  others  in  every 
direction.^  ^ 


A 


APPENDIX 

In  the  following  citations  from  the  recent  works  of  friends  all  but  one 
of  which  have  come  into  the  author's  hands  since  the  present  volume 
was  written,  the  reader  will  find  not  only  an  amplification  by  Gies  (Note  I) 
and  Loeb  (Notes  III  and  IV)  of  certain  passages  in  the  text,  but  in  Notes 
V  and  VI  original  views  previously  and  independently  expressed  by 
ALithews,  which  are  somewhat  similar  to  those  the  author  has  developed 
under  the  law  of  interaction. 

NOTE  I 

DIFFERENT   MODES   OF   STORAGE   AND  RELEASE   OF  ENERGY  IN  LIVING 

ORGANISMS^ 

"The  elements  referred  to"  (''This  energy  is  distributed  among  the 
eighty  or  more  chemical  elements  of  the  sun  and  other  stars,"  p.  i8)  ''are 
available  to  plants,  in  the  first  place,  in  the  form  of  compound  substances 
only,  simple  though  those  substances  are,  such  as  water,  carbon  dioxid, 
nitrate,  phosphate,  etc.  When  these  substances  are  taken  from  the  air 
and  soil  into  plants  they  are  reduced  in  the  main,  that  is,  the  elements  are 
combined  there  into  new  groupings  with  a  storage  of  energy,  the  effective 
radiant  kinetic  energy  from  the  sun  becoming  potential  energy  in  the  con- 
stituents of  plants.  Plant  substances  are  eaten  by  herbivorous  animals, 
that  is  to  say,  these  substances  are  hydrolyzed  and  oxidized  in  such 
animals;  the  elements  are,  in  the  main,  'burst  asunder'  into  new  group- 
ings, with  the  release  of  energy,  the  stored  potendal  energy  becoming 
kinetic.  Carnivorous  and  omnivorous  animals  obtain  plant  substances, 
either  directly  or  in  the  form  of  animal  matter  from  herbivorous  animals, 
thus,  in  effect,  doing  what  herbivorous  animals  do,  namely,  using  plant 
substances  by  disintegrating  them  with  the  release  of  energy." 

NOTE  II 

BLUE-GREEN  ALG^  POSSIBLY  AMONG  THE   FIRST   SETTLERS  OF  OUR 

PLANET 2 

"In  1883  the  small  island  of  Krakatau  w^as  destroyed  by  the  most  vio- 
lent volcanic  eruption  on  record.  A  visit  to  the  islands  two  months  after 
the  eruption  showed  that  'the  three  islands  were  covered  with  pumice 

^  W.  J.  Gies,  letter  of  May  16,  191 7. 
2  Loeb,  Jacques,  1916,  Tlie  Organism  as  a  Whole,  p.  21. 

285 


286 


APPENDIX 


and  layers  of  ash  reaching  on  an  average  a  thickness  of  thirty  metres,  and 
frequently  sixty  metres.* ^  Of  course  all  life  on  the  islands  was  extinct. 
When  Treub  in  1886  first  visited  the  island,  he  found  that  blue-green  algae 
were  the  first  colonists  on  the  pumice  and  on  the  exposed  blocks  of  rock 
in  the  ravines  on  the  mountain-slopes.  Investigations  made  during  sub- 
sequent expeditions  demonstrated  the  association  of  diatoms  and  bac- 
teria "  [with  the  algae].  '^  All  of  these  were  probably  carried  by  the  wind. 
The  algae  referred  to  w^re  according  to  Euler  of  the  nostoc  type.  Nostoc 
does  not  require  sugar,  since  it  can  produce  that  compound  from  the  CO, 
of  the  air  by  the  activity  of  its  chlorophyll.  This  organism  possesses  also 
the  power  of  assimilating  the  free  nitrogen  of  the  air.  From  these  obser- 
vations and  because  the  Nostocacece  generally  appear  as  the  first  settlers 
on  sand  the  conclusion  has  been  drawn  that  they  or  the  group  of  Schizo- 
phycecB  to  which  they  belong  formed  the  first  settlers  of  our  planet." ^ 

• 

NOTE  III 

ONE   SECRET   OF   LIFE — SYNTHETIC  TRANSFORMATION   OF  INDIFFERENT 

MATERIAL^ 

"The  essential  difference  between  living  and  non-living  matter  con- 
sists then  in  this:  the  living  cell  synthetizes  its  own  complicated  specific 
material  from  indifferent  or  non-specific  simple  compounds  of  the  sur- 
rounding medium,  while  the  crystal  simply  adds  the  molecules  found  in 
its  supersaturated  solution.  This  synthetic  power  of  transforming  small 
*  building  stones'  into  the  complicated  compounds  specific  for  each  or- 
ganism is  the  'secret  of  life'  or  rather  one  of  the  secrets  of  life." 

NOTE  IV 

INTERACTION  THROUGH  CATALYSIS — THE  ACCELERATION  OF  CHEMICAL 

REACTIONS  THROUGH  THE  PRESENCE  OF  ANOTHER  SUBSTANCE 

WHICH  IS  NOT  CONSUMED  BY  THE  REACTION* 

"The  discovery  of  Lavoisier  and  La  Place  left  a  doubt  in  the  minds 
of  scientists  as  to  whether  after  all  the  dynamics  of  oxidations  and  of 
chemical  reactions  in  general  is  the  same  in  Hving  matter  and  in  inanimate 
matter.  .  .  .  The  way  out  of  the  difficulty  was  shown  in  a  remarkable 
article  by  Berzelius.^      He  pointed  out  that  in  addition  to  the  forces  of 

*  Ernst,  A.,  The  New  Flora  of  the  Volcanic  Island  of  Krakatau,  Cambridge,  1908. 

2  Euler,  H.,  Pflanzenc hemic,  1909,  ii  and  iii,  140. 

3  Loeb,  Jacques,  1916.     The  Organism  as  a  Whole,  p.  23. 

*  Loeb,  Jacques,  1906.     The  Dynamics  of  Living  Matter,  pp.  7,  8. 

^  Berzelius,  Einige  Ideen  iiber  cine  bei  der  Bildung  organischer  Verhindungen  in  der 
lehenden  Natur  unrksame  aber  bisher  nicht  bemerkte  Kraft.  Berzelius  u.  VVoehler, 
Jahresbericht,  1836. 


APPENDIX 


287 


affinity,  another  force  is  active  in  chemical  reactions:  this  he  called  cata- 
lytic force.  As  an  example  he  used  Kirchhoff's  discovery  of  the  action  of 
dilute  acids  in  the  hydrolysis  of  starch  to  dextrose.  In  this  process  the 
acid  is  not  consumed,  hence  Berzelius  concluded  that  it  did  not  act  through 
its  affinity,  but  merely  by  its  presence  or  its  contact.  ...  He  then  suggests 
that  the  specific  and  somewhat  mysterious  reactions  in  Uving  organisms 
might  be  due  to  such  catalytic  bodies  as  act  only  by  their  presence,  without 
being  consumed  in  the  process.  He  quotes  as  an  example  the  action  of 
diastase  in  the  potato.  ^In  animals  and  plants  there  occur  thousands 
of  catalytic  processes  between  the  tissues  and  the  Hquids.'  The  idea  of 
Berzelius  has  proved  fruitful.  ...  We  now  know  that  we  have  no  right 
to  assume  that  the  catalytic  bodies  do  not  participate  in  the  chemical 
reaction  because  their  quantity  is  found  unaltered  at  the  end  of  the  reac- 
tion. On  the  contrary,  we  shall  see  that  it  is  probable  that  they  can  ex- 
ercise their  influence  only  by  participating  in  the  reaction,  and  by  form- 
ing intermediary  compounds,  which  are  not  stable.  The  catalyzers  may 
be  unaltered  at  the  end  of  the  reaction,  and  yet  participate  in  it. 

"In  addition  we  owe  to  Wilhelm  Ostwald^  the  conception  that  the  cata- 
lyzer does  not  as  a  rule  initiate  a  reaction  which  otherwise  would  not  occur, 
but  only  accelerates  a  reaction  which  otherwise  would  indeed  occur,  but 
too  slowly  to  give  noticeable  results  in  a  short  time." 


NOTE  V 

THE   CAUSES   OR   AGENTS  OF   SPEED  AND  ORDER  IN  THE   REACTIONS 
OF   LIVING  BODIES — ENZYMES,   COLLOIDS,   ETC.* 

*' There  is  still  another  feature  of  cell  chemistry  which  must  strike  even 
the  most  superficial  observer,  and  that  is  the  speed  with  which  growth 
and  the  chemical  reactions  occur  in  it.  .  .  .  Starch  boiled  with  water 
does  not  easily  take  on  water  and  split  into  sweet  glucose,  but  in  the  plant 
cell  it  changes  into  sugar  under  appropriate  conditions  very  rapidly.  How 
does  it  happen  then  that  the  chemical  changes  of  the  foods  go  on  so  rapidly 
in  living  matter  and  so  slowly  outside?  This  is  owing  to  the  fact,  as  we 
now  know,  that  Hving  matter  always  contains  a  large  number  of  sub- 
stances, or  compounds,  called  enzymes  (Gr.  en,  in;  zyme,  yeast;  in  yeast) 
because  they  occur  in  a  striking  way  in  yeast.  These  enzymes,  which  are 
probably  organic  bodies,  but  of  which  the  exact  composition  is  as  yet 
unknown,  have  the  property  of  greatly  hastening,  or  as  is  generally  said, 
catalyzing,  various  chemical  reactions.  The  word  catalytic  {kaUiy  down; 
lysis,  separation)  means  literally  a  dow^n  separation  or  decomposition,  but 

^Ostwald,  W.,  Lehrbuch  der  allgemeinen  Chemie,  vol.  II,  2d  part,  p.  248,  1902. 
2  Mathews*  Albert  P.,  Physiological  Chemistry ^  pp.  10-12. 


288 


APPENDIX 


it  is  used  to  designate  any  reaction  which  is  hastened  by  a  third  substance, 
this  third  substance  not  appearing  much,  if  at  all,  changed  in  amount  at 
the  end  of  the  reaction.  Living  matter  is  hence  peculiar  in  the  speed  with 
which  these  hydrolytic,  oxidative,  reduction,  or  condensation  reactions 
occur  in  it;  and  it  owes  this  property  to  various  substances,  catalytic 
agents,  or  enzymes,  found  in  it  everywhere.  Were  it  not  for  these  sub- 
stances reactions  would  go  on  so  slowly  that  the  phenomena  of  life  would 
be  quite  different  from  what  they  are.  Since  these  catalytic  substances 
are  themselves  produced  by  a  chemical  change  preceding  that  which  they 
catalyze,  we  might,  perhaps,  call  them  the  memories  of  those  former  chem- 
ical reactions,  and  it  is  by  means  of  these  memories,  or  enzymes,  that 
cells  become  teachable  in  a  chemical  sense  and  capable  of  transacting 
their  chemical  affairs  with  greater  efficiency.  Whether  all  our  memories 
have  some  such  basis  as  this  we  cannot  at  present  say,  since  we  do  not 
yet  know  anything  of  the  physical  basis  of  memory. 

"Living  reactions  have  one  other  important  peculiarity  besides  speed, 
and  that  is  their  ^orderliness.''  The  cell  is  not  a  homogeneous  mixture  in 
which  reactions  take  place  haphazard,  but  it  is  a  well-ordered  chemical 
factory  with  specialized  reactions  occurring  in  various  parts.  If  proto- 
plasm be  ground  up,  thus  causing  a  thorough  intermixing  of  its  parts,  it 
can  no  longer  live,  but  there  results  a  mutual  destruction  of  its  various 
structures  and  substances.  The  orderliness  of  the  chemical  reactions  is 
due  to  the  cell  structure;  and  for  the  phenomena  of  life  to  persist  in  their 
entirety  that  structure  must  be  preserved.  It  is  true  that  in  such  a  ground- 
up  mass  many  of  the  chemical  reactions  are  presumably  the  same  as  those 
which  went  on  while  structure  persisted,  but  they  no  longer  occur  in  a 
w^U-regulated  manner;  some  have  been  checked,  others  greatly  increased 
by  the  intermixing.  This  orderliness  of  reactions  in  living  protoplasm  is 
produced  by  the  specialization  of  the  cell  in  different  parts.  .  .  .  Thus 
the  nuclear  wall,  or  membrane,  marks  oflf  one  very  important  cell  region 
and  keeps  the  nuclear  sap  from  interacting  with  the  protoplasm.  Pro- 
found, and  often  fatal,  changes  sometimes  occur  in  cells  when  an  admix- 
ture of  nuclear  and  cytoplasmic  elements  is  artificially  produced  by  rup- 
ture of  this  membrane.  Other  localizations  and  organizations  are  due  to 
the  colloidal  nature  of  the  cell-protoplasm  and  possibly  to  its  lipoid  char- 
acter. By  a  colloid  is  meant,  Hterally,  a  glue-Uke  body;  a  substance  which 
will  not  diffuse  through  membranes  and  which  forms  with  water  a  kind 
of  tissue,  or  gel.  It  is  by  means  of  the  colloids  of  a  protein,  lipoid,  or  car- 
bohydrate nature  which  make  up  the  substratum  of  the  cell  that  this 
localization  of  chemical  reactions  is  produced;  the  colloids  furnish  the 
basis  for  the  organization  or  machinery  of  the  cell;  and  in  their  absence 
there  could  be  nothing  more  than  a  homogeneous  conglomeration  of  re- 
actions.    The  properties  of  colloids  become,   therefore,  of  the  greatest 


APPENDIX 


289 


importance  in  interpreting  cell  life,  and  it  is  for  this  reason  that  they  have 
been  studied  so  keenly  in  the  past  ten  years.  The  colloids  localize  the  cell 
reactions  and  furnish  the  physical  basis  of  its  physiology;  they  form  the 
cell  machinery." 


NOTE  VI 

INTERACTIONS  OF  THE  ORGANS  OF  INTERNAL  SECRETION  AND  HEREDITY ^ 

The  following  table  expresses  the  action  of  some  of  the  organs  of  internal 
secretion : 


On  Protein  Metabolism 
Stimulating 
(accelerating) 
Thyroid 
Pituitary  body 
Suprarenal    glands    and    other 

adrenalin-secreting  tissue 
Reproductive  glands 


On  Calcium  Retention 


Favorable  to 
Pituhary  body 
Thyroids 
Parathyroids 


Inhibiting 
(retarding) 

Pancreas 

Parathyroids 


Inhibiting 
Reproductive  glands 


The  facts  that  are  here  presented  show  that  the  action  of  the  anterior 
lobe  of  the  pituitary  body  upon  the  chemical  changes  or  transformations 
taking  place  in  the  vertebrate  organism  or  in  any  of  its  cells  strongly  re- 
sembles the  action  of  the  thyroid,  although  less  pronounced.  It  is  clear 
from  its  relation  to  the  reproductive  organs,  to  the  adrenalin-secreting 
tissues  of  the  suprarenal  glands  and  other  similar  tissues,  and  to  the 
formation  of  an  abnormal  amount  of  glucose  in  the  urine,  that  the 
pituitary  body,  thyroids,  reproductive  glands,  suprarenals,  and  thymus 
are  a  closely  related  series  of  organs  which  mutually  influence  each  other's 
growth. 

Important  as  these  organs  are,  it  must  be  remembered  that  the  co- 
ordination of  all  the  chemical  changes  and  transformations  within  the 
body— all  processes  of  renewal,  change,  or  disorganization  such  as  respira- 
tion, nutrition,  excretion,  etc. — embraces  every  organ  in  it.  The  body  is 
an  organic  whole,  and  the  so-called  organs  of  internal  secretion  are  not 
unique,  but  the  bones,  muscles,  skin,  brain,  and  every  part  of  the  body  are 
furnishing  internal  secretions  necessary  to  the  development  and  proper 

'Mathews,  Albert  P.,  1916.      Physiological  Chemistry,  pp.  649,  650  (modified). 


290 


APPENDIX 


functioning  of  all  the  other  organs  of  the  body.  A  scheme  of  the  organs 
of  internal  secretion,  to  be  complete,  must  embrace  every  organ,  and  so 
far  only  the  barest  beginning  has  been  made  in  this  study  so  important, 
so  necessary  for  the  understanding  of  development  and  mhentance.  Prob- 
lems of  development  and  inheritance  cannot  be  solved  until  these  physio- 

loeical  questions  are  answered.  . 

As  for  the  bearing  of  these  processes  upon  Heredity,  the  internal  secre- 
tions of  the  body  appear  to  Mathews  to  constitute  strong  evidence  against 
the  existence  of  such  things  as  inheritance  by  means  of  structural  units 
in  the  germ  which  represent  definite  characters  in  the  body.     We  see  in 
the  internal  secretions,  he  observes,  that  every  character  in  the  body  involves 
a  large  number  of  factors  {i.  e.,  determiners).     The  shape  and  size  of  the 
body,  the  coarseness  of  the  hair,  the  persistence  of  the  milk-teeth,  a  ten- 
dency toward  fatness-all  these  may  easily  depend  on  the  pituitary  body, 
on  the  thyroid,  and  on  the  reproductive  organs,  and  these-in  their  turn 
—are  but  the  expression  of  other  influences  played  upon  them  by  their 
surroundings  and  their  own  constitution.    An  accurate  examination  shows 
the  untrustworthiness  of  any  such  simple  or  naive  view  as  that  of  unit 
characters. 

NOTE  VII 

TABLE— RELATIONS  OF  THE  PRINCIPAL   GROUPS  OF   ANIMALS 

REFERRED   TO   IN   THE   TEXT 


Phylum 

Class 

Protozoa 

'  iRhizopoda 

(the  simplest 

animals) 

PAGES 


f  Lobosa— .4m<Ffta,  etc 93»  112, 114,  "6 

Foraminifera  (porous-shelled  protozoa) 
\                                                                32,103,115 
[  Radiolaria  (siliceous-shelled  protozoa) "5 

Mastigophora "/'  \\\ 

Infusoria— ciliates,  etc "^'  "^ 

Sporozoa 


PORIFERA 

(sponges) 


CCELENTERATA 


{ 


^Calcarea  Calcareous  sponges 

iNon-Calcarea      f  Siliceous 

\  Fibrous 


I 


^  Hydrozoa 


^Scyphozoa 
^Actinozoa 
Ctenophora 


130 


"3 


{Hydroids — millepores 
Siphonophores 
Graptolithida 

Jellyfishes 120, 129.  130 

Sea-anemones,  corals,  sea-fans,  etc 103 


1  Fossil  and  recent  forms.  ^  -i    .  * 

All  other  classes  listed  are  as  yet  unknown  m  the  fossil  state. 


APPENDIX 


291 


Phylum 
Platyhelminthes 


Class 
Turbellaria 
Trematoda 
Cestoda 


PAGES 


Flat  worms 
Flukes 
Tape- worms 


Nemathelminthes  I    Nematoda  Round  worms 

Acanthocephala     Hook-headed  worms 
'  Chsetognatha         Arrow-worms 


120, 129 


Trochelminthes 


MOLLUSCOIDA 


Echinodermata 


Annulata 

(true  worms) 


Rotifera 

^  Polyzoa 
Phoronida 
^  Brachiopoda 

^  Asteroidea 
^  Ophiuroidea 
^  Echinoidea 
^  Holothuroidea 
^Crinoidea 
^Cystoidea  1 
2BlastoideaJ 


^  Chaetopoda 
Gephyrea 
Hirudinea 


Wheel-animalcules 

Bryozoa  (moss  animals) 

Lamp-shells 120, 123, 130, 138, 140 

Sea-stars,  starfishes 136,  172 

Brittle  stars 

Sea-urchins 94 

Sea-cucumbers 125, 127 

Sea-lilies  (stone-lilies) 66 

primitive  echinoderms 

Sea- worms,  earthworms 128 

Sipunculids 
Leeches 


Arthropoda 


Branchiata 
[  ^Crustacea 


I 


2Trilobita 
^Xiphosura 


Tracheata 

Onychophora 
^  Myriapoda 
1  ^Arachnoidea 
\  ^Insecta 


Crabs,  lobsters,  shrimp,  barnacles,  ostra- 

cods 120, 124,134 

Trilobites,  eurypterids 121, 125, 132, 133 

Horseshoe  crabs 124, 125, 132 


Peripatus 

Centipedes,  millepedes 

Spiders,  scorpions,  mites,  ticks.  . .  .130, 132, 136 

Insects 105, 130, 136,  254 


MOLLUSCA 


'  iPelycypoda  Clams,  oysters,  mussels 130 

'Amphineura  Chitons 

<   ^Gastropoda  Limpets,  snails,  slugs,  sea-hares,  etc 120,130 

^Scaphopoda  Tusk-shells 

^Cephalopoda  Nautilus,  cuttle-fish,  ammonites.  . .  130, 137-139 


*  Fossil  and  recent  forms. 

2  Extinct  fossil  forms. 

All  other  classes  listed  are  as  yet  unknown  in  the  fossil  state. 


292 

Phylum 
Chordata 

Sub-phylum 
Adelochorda . . 
Urochorda.    . 


APPENDIX 


Class 


PAGES 


Vertebrata 


Acrania 
Cyclostomata 
*  Pisces 
(fishes) 


^Amphibia 
'  Reptilia 


Balanoglossus,  etc. — worm-like  chordates 
Ascidians,  salps,  etc. — sessile  and  secon- 
darily free-swimming  marine  chordates, 

162,  168 

Amphioxus  (lancelets) 162 

Lampreys,  hags 168 

Ostracodermata  (Palaeozoic  shelly-skinned 

fishes) 161 ,  165-168 

Arthrodira  (Palaeozoic  joint-necked  fishes) 

166-168 
Elasmobranchii — sharks,  rays,  chimaeroids 

161,  167-169 

Dipnoi  (lung-fishes) 168, 170, 172 

Teleostomi 1 73 

lobe-finned  ganoids  (Crossopterygii) 

168,  172,174 
true     ganoids — sturgeons,     garpike, 

bowfins,  etc 168, 1 70 

teleosts  (bony  fishes) 168, 170, 175 

Frogs,  toads,  newts,  mud-puppies,  Stego- 
cephalia,  etc 177-183 

Turtles,  tortoises,  tuateras,  lizards,  mosa- 
saurs,  snakes,  crocodilians,  dinosaurs, 
mammal-like  reptiles,  ichthyosaurs,  ple- 
siosaurs,  pterosaurs  (flying  reptiles),  etc. 

184-226 

f  Reptile-like  birds  {ArchcEopteryx) 226-229 

\  Modernized  birds 227-231 

f  "Ratite"  birds — ostriches,  moas,  etc. 

228,  229 
"Carinate"  birds — toothed  birds  and 
all  other  birds 230,  231 

[^Mammalia  [  Monotremes      (egg-laying      mammals) — 

duck-bills,  etc 235,  273 

Marsupials  (pouched  mammals) — opos- 
sums, kangaroos,  etc 235,  237,  243,  244 

Placentals 

insectivores,  carnivores,  primates,  ro- 
dents, bats,  whales,  artiodactyls  (cattle, 
deer,  pigs,  antelopes,  giraffes,  camels, 
hippopotami,  etc.),  ungulates  including 
proboscidea  (mastodons  and  elephants) 
and  perissodactyls  (horses,  tapirs,  rhi- 
noceroses, titanotheres,  etc.),  and  many 
other  orders 259-274 

'  Fossil  and  recent  forms. 
All  other  classes  listed  are  as  yet  unknown  in  the  tossil  state. 


^Aves 
(birds) 


BIBLIOGRAPHY 

INTRODUCTION 

Campbell,  William  Wallace. 

191 5  The  Evolution  of  the  Stars  and  the  Formation  of  the  Earth.     Sec- 

(1914)  ond  series  of  lectures  on  the  William  Ellery  Hale  foundation, 
delivered  December  7  and  8,  1914.  Pop.  Sci.  Mon.,  September, 
191 5,  pp.  209-235;  Scientific  Monthly,  October,  191 5,  pp.  1-17; 
November,  1915,  pp.  177-194;  December,  1915,  pp.  238-255. 

Chamberlin,  Thomas  Chrowder. 

1916  The  Evolution  of  the  Earth.     Third  series  of  lectures  on  the  William 

(191 5)  Ellery  Hale  foundation,  delivered  April  19-21,  191 5.  Scientific 
Monthly,  May,  1916,  pp.  417-437;  June,  1916,  pp.  536-556. 

Clarke,  Frank  Wigglesworth. 

1873  Evolution  and  the  Spectroscope.  Pop.  Sci.  Mon.,  January,  1873, 
pp.  320-326. 

Crile,  George  W. 

1 916      Man — An  Adaptive  Mechanism.     Macmillan  Co.,  New  York,  191 6. 

Cushlng,  Harvey. 

191 2  The  Pituitary  Body  and  its  Disorders,  Clinical  States  Produced  by 
Disorders  of  the  Hypophysis  Cerebri.  Harvey  Lecture,  delivered 
in  1910,  amplified.  J.  B.Lippincott  Co.,  Philadelphia  and  Lon- 
don, 1912. 

Davies,  G.  R. 

1916  Plato's  Philosophy  of  Education.  School  and  Society,  April  22,  1916, 
pp.  582-585. 

Eucken,  Rudolf. 

191 2  Main  Currents  of  Modern  Thought.     Transl.  by  Meyrick  Booth. 

Charles  Scribner's  Sons,  New  York,  191 2. 

Goodale,  H.  D. 

1 9 16  Gonadectomy  in  Relation  to  the  Secondary  Sexual  Characters  of 
Some  Domestic  Birds.  Carnegie  Institution  of  Washington, 
Publ.  no.  243,  Washington,  1916. 

Henderson,  Lawrence  J. 

1913  The   Fitness  of   the   Environment.     Macmillan   Co.,   New  York, 

1913- 

293 


294 


BIBLIOGRAPHY 


James,  William. 

1902  The  Varieties  of  Religious  Experience,  a  Study  in  Human  Nature. 
Fourth  impression.  Longmans,  Green  Co.,  London  and  Bom- 
bay, 1902. 

Morgan,  Thomas  Hunt. 

191 5  The  Constitution  of  the  Hereditary  Material.     Proc.  Amer.  Phil, 

Soc,  May-July,  191 5,  pp.  i43-i53- 

1916  A  Critique  of  the  Theory  of  Evolution.     The  Louis  Clark  Vanuxem 

foundation  lectures  for  1915-1916.  Princeton  University  Press, 
Princeton;  Humphrey  Milford,  London;  Oxford  University  Press, 
1916. 

Osborn,  Henry  Fairfield. 

1894      From  the  Greeks  to  Darwin.     Macmillan  Co.,  New  York,  1894. 

191 2  Tetraplasy,  the  Law  of  the  Four  Inseparable  Factors  of  Evolution. 
Jour.  Acad.  Nat.  Sci.  Phila.,  Special  volume  published  in  com- 
memoration of  the  One  Hundredth  Anniversary  of  the  Founding 
of  the  Academy,  March  21,  191 2.     Issued  September  14,  1912, 

pp.  275-309.  .       . 

191 7  Application  of  the  Laws  of  Action,  Reaction,  and  Interaction  in 

Life  Evolution.     Proc.  National  Acad.  Sci.,  January,  191 7,  pp.  7-9. 

Rutherford,  Sir  Ernest.  » 

191 5      The  Constitution  of  Matter  and  the  Evolution  of  the  Elements. 

(1914)  First  series  of  lectures  on  the  William  EUery  Hale  foundation,  de- 
livered April,  1914.     Pop.  Sci.  Mon.,  August,  191 5,  pp.  105-142. 

CHAPTER  I 
Becker,  George  F. 

1910      The  Age  of  the  Earth.     Smithsonian  Misc.  Colls.,  vol.  56,  no.  6, 
Publ.  no.  1936,  Washington,  1910. 

1915  Isostasy  and  Radioactivity.     Bim.  Geol.  Soc.  Amer.,  March,  1915, 

pp.  171-204. 

Chamberlin,  Thomas  Chrowder. 

1916  The  Evolution  of  the  Earth.     Third  series  of  lectures  on  the  Wil- 

(191 5)  liam  Ellery  Hale  foundation,  delivered  April  19-21,  1915-  Scien- 
tific Monthly,  May,  1916,  pp.  417-437;  June,  1916,  pp.  536-556. 

Clarke,  Frank  Wigglesworth. 

1916  The  Data  of  Geochemistry.  Third  edition.  U.  S.  Geol.  Survey, 
Bull.  491.     Gov't  Printing  Office,  Washington,  1916. 

Cuvier,  Baron  Georges  L.  C.  F.  D. 

1825  Discours  sur  les  revolutions  de  la  surface  du  globe  et  sur  les  chan- 
gemens  qu'elles  ont  produit  dans  le  regne  animal.  See  Recherches 
sur  les  Ossemens  fossiles.  Third  edition,  vol.  I,  G.  Dufour  et  E. 
d'Ocagne,  Paris,  1825,  pp.  1-172. 


BIBLIOGRAPHY 


29s 


Henderson,  Lawrence  J. 

1913      The  Fitness  of  the  Environment.     Macmillan  Co.,  New  York,  1913. 

Button,  James. 

1795  Theory  of  the  Earth  with  Proofs  and  Illustrations.  Edinburgh, 
1795- 

Jordan,  Edwin  O. 

1908  A  Text-Book  of  General  Bacteriology.  W.  B.  Saunders,  Phila- 
delphia and  London,  1908. 

Judd,  John  W. 

1910  The  Coming  of  Evolution.  The  Story  of  a  Great  Revolution  in 
Science.  Cambridge  Manuals  of  Science  and  Literature,  Cam- 
bridge University  Press,  Cambridge,  1910. 

Loeb,  Jacques. 

1906  The  Dynamics  of  Living  Matter.  Columbia  University  Press, 
New  York,  1906. 

Lyell,  Charles. 

1830      Principles  of  Geology.     Murray,  London,  1830. 

Moulton,  F.  R. 

191 2  Descriptive  Astronomy.  Amer.  School  of  Correspondence,  Chicago, 
1912. 

Pirsson,  Louis  V.,  and  Schuchert,  Charles. 

191 5  A  Text-Book  of  Geology.  Part  I,  Physical  Geology,  by  Louis  V. 
Pirsson.  Part  II,  Historical  Geology,  by  Charles  Schuchert. 
John  Wiley  &  Sons,  New  York;  Chapman  &  Hall,  London,  191 5. 

Poulton,  Edward  B. 

1896  A  Naturalist's  Contribution  to  the  Discussion  upon  the  Age  of  the 
Earth.  Pres.  Addr.  Zool.  Sec.  Brit.  Ass.,  delivered  September  17, 
1896.     Kept.  Brit.  Ass.,  Liverpool,  1896,  pp.  808-828. 

Rutherford,  Sir  Ernest. 

1906  Radioactive  Transformations.  Charles  Scribner's  Sons,  New  York, 
1906. 

Schuchert,  Charles. 

191 5      A  Text-Book  of  Geology  (with  Pirsson,  Louis  V.).     See  Pirsson. 

Walcott,  Charles  D. 

1893  Geologic  Time,  as  indicated  by  the  sedimentary  rocks  of  North 
America.     Jour.  Geol.,  October-November,  1893,  pp.  639-676. 


I 


,1 


296 


BIBLIOGRAPHY 


CHAPTER  II 
Abel,  John  J. 

1 91 5  Experimental  and  Chemical  Studies  of  the  Blood  with  an  Appeal 

for  More  Extended  Chemical  Training  for  the  Biological  and 
Medical  Investigator.  First  Mellon  Lecture,  Soc.  Biol.  Res., 
Univ.  Pittsburgh.    Science^  August  6,  191 5,  pp.  165-178. 

Bechhold,  Heinrich. 

191 2  Die  Kolloide  in  Biologie  und  Medizin.     Theodor  Steinkopf,  Dres- 

den, 191 2. 

Biedl,  Artur. 

1913  The  Internal  Secretory  Organs:    Their  Physiology  and  Pathology. 

Transl.  by  Linda  Forster.     William  Wood  &  Co.,  New  York,  1913. 

Calkins,  Gary  N. 

1 91 6  General  Biology  of  the  Protozoan  Life  Cycle.     Amer.  Naturalist, 

May,  1916,  pp.  257-270. 

Cunningham,  J.  T. 

1908  The  Heredity  of  Secondary  Sexual  Characters  in  Relation  to  Hor- 
mones, a  Theory  of  the  Heredity  of  Somatogenic  Characters. 
Archiv  fiir  Entwickliingsmechanik,  November  24,  1908,  pp.  372- 
428. 

Gushing,  Harvey. 

191 2  The  Pituitary  Body  and  its  Disorders,  Clinical  States  Produced  by 

Disorders  of  the  Hypophysis  Cerebri.  Harvey  Lecture,  1910, 
amplified.    J.B.Lippincott  Co.,  Philadelphia  and  London,  191 2. 

Cuvier,  Baron  Georges  L.  C.  F.  D. 

181 7  Le  Regne  animal  distribue  d'apres  son  Organisation.  Tome  I, 
contenant  introduction,  les  mammiferes  et  les  oiseaux.  Deter- 
ville,  Paris,  181 7.  , 

Hedin,  Sven  G. 

191 5      Colloidal  Reactions  and  Their  Relations  to  Biology.     Harvey  Lec- 
(1914)         ture,   delivered  January   24,   1914.     See    The  Harvey  Lectures, 
1913-1914,  J.B.Lippincott  Co.,  Philadelphia,  1915,  pp.  162-173. 

Henderson,  Lawrence  J. 

1913  The  Fitness  of  the  Environment.     Macmillan  Co.,  New  York,  1913. 

Jordan,  Edwin  O. 

1908  A  Text-Book  of  General  Bacteriology.  W.  B.  Saunders,  Philadel- 
phia and  London,  1908. 

Loeb,  Jacques. 

1906  The  Dynamics  of  Living  Matter.  Columbia  University  Press, 
New  York,  1906. 


m 


BIBLIOGRAPHY 


297 


Loeb,  Leo. 

19 16  The  Scientific  Investigation  of  Cancer.  Scientific  Monthly ,  Sep- 
tember, 1916,  pp.  209-226. 

Moore,  F.  J. 

191 5  Outlines  of  Organic  Chemistry.  John  Wiley  &  Sons,  New  York 
and  London,  191 5. 

Osbom,  Henry  Fairfield. 

1895  The  Hereditary  Mechanism  and  the  Search  for  the  Unknown  Fac- 

tors of  Evolution.     Amer.  Naturalist,  May,  1895,  pp.  418-439. 

Pirsson,  Louis  V.,  and  Schuchert,  Charles. 

191 5  A  Text-Book  of  Geology.  Part  I,  Physical  Geology,  by  Louis  V. 
Pirsson.  Part  II,  Historical  Geology,  by  Charles  Schuchert. 
John  Wiley  &  Sons,  New  York;   Chapman  &  Hall,  London,  191 5. 

Poulton,  Edward  B. 

1896  A  Naturalist's  Contribution  to  the  Discussion  upon  the  Age  of  the 

Earth.     Pres.  Addr.  Zool.  Sec.  Brit.  Ass.,  delivered  September 
17,  1896.     Rept.  Brit.  Ass.,  Liverpool,  1896,  pp.  808-828. 

Richards,  Herbert  M. 

191 5  Acidity   and   Gas  Interchange   in   Cacti.     Carnegie  Institution  of 

Washington,  Publ.  no.  209,  Washington,  191 5. 

Russell,  H.  N. 

1916  On  the  Albedo  of  the  Planets  and  their  Satellites.     Proc.  National 

Acad.  Sci.,  February  15,  1916,  pp.  74-77. 

Rutherford,  Sir  Ernest. 

191 5  The  Constitution  of  Matter  and  the  Evolution  of  the  Elements. 
(1914)         First  series  of  lectures  on  the  William  Ellery  Hale  foundation, 

delivered  April,  1914.     Pop.  Sci.  Mon.,  August,  191 5,  pp.  105-142. 

Sachs,  Julius. 

1882  A  Text-Book  of  Botany,  Morphological  and  Physiological.  Claren- 
don Press,  Oxford,  1882. 

de  Saussure,  N.  T. 

1804      Recherches  chimiques  sur  la  Vegetation.     Paris,  1804. 

Schafer,  Sir  Edward  A. 

1916  The  Endocrine  Organs,  an  Introduction  to  the  Study  of  Internal 

Secretion.     Longmans,  Green  &  Co.,  London,  New  York,  Bom- 
bay, Calcutta,  Madras,  1916. 

Schuchert,  Charles. 

191 5      A  Text-Book  of  Geology  (with  Pirsson,  Louis  V.).     See  Pirsson. 


298 


BIBLIOGRAPHY 


Smith,  Alexander. 

1914  A  Text-Book  of  Elementary  Chemistry.     The  Century  Co.,  New 

York,  1914. 

Wilson,  Edmund  B. 

1906      The  Cell  in  Development  and  Inheritance.     Second  edition.     Mac- 
millan  Co.,  New  York,  1906. 

Zinsser,  Hans. 

191 5  The   More   Recent   Developments   in   the   Study  of   Anaphylactic 
(1914)         Phenomena.     Harvey    Lecture,     delivered    January     30,    1914- 

Archives  of  Internal  Medicine,  August,  191 5»  PP-  223-256. 

1916  Infection  and  Resistance.     Macmillan  Co.,  New  York,  1916. 

CHAPTER  III 

Barnes,  Charles  Reid. 

1910  A  Text-Book  of  Botany  for  Colleges  and  Universities  (with  Coulter, 
John  Merle,  and  Cowles,  Henry  Chandler).     See  Coulter. 

Berry,  Edward  Wither. 

1914  The  Upper  Cretaceous  and  Eocene  Floras  of  South  Carolina  and 
Georgia.  U.  S.  GeoL  Survey.  Professional  Paper  no.  84.  Gov't 
Printing  Ofhce,  Washington,  1914. 

Clarke,  Frank  Wigglesworth. 

1916  The  Data  of  Geochemistry.  Third  edition.  U.  S.  GeoL  Survey, 
Bull.  491.     Gov't  Printing  Othce,  Washington,  1916. 

Coulter,  John  Merle;  Barnes,  Charles  Reid;  and  Cowles,  Henry  Chandler. 
1910      A  Text-Book  of  Botany  for  Colleges  and  Universities.     American 
Book  Co.,  New  York,  Cincinnati,  Chicago,  1910. 

Cowles,  Henry  Chandler. 

1910  A  Text-Book  of  Botany  for  Colleges  and  Universities  (with  Coulter, 
John  Merle,  and  Barnes,  Charles  Reid).     See  Coulter. 

Czapek,  Friedrich. 

1913  Biochemie  der  Pflanzen.     Second  edition,  revised.     Gustav  Fischer, 

Jena,  1913. 

Drew,  George  H. 

1914  On  the  Precipitation  of  Calcium  Carbonate  in  the  Sea  by  Marine 

Bacteria.     Papers  from  the  Tortugas  Laboratory,  Carnegie  Insti- 
tution of  Washington,  vol.  V,  1914,  pp.  7-45- 

Driesch,  Hans. 

1908  The  Science  and  Philosophy  of  the  Organism.  The  GifTord  Lectures 
delivered  before  the  University  of  Aberdeen  in  the  years  1Q07  and 
1908.  Vols.  I  (1907)  and  II  (1908).  Adam  and  Charles  Black, 
London,  1908. 


BIBLIOGRAPHY 


299 


Fischer,  Alfred. 

1900      The  Structure  and  Functions  of  Bacteria. 
Jones.     Clarendon  Press,  Oxford,  1900. 


Transl.  by  A.  Coppen 


Harder,  E.  C. 

1915      Iron  Bacteria.     Science,  September  3,  1915,  pp.  310^  3ii- 

Harvey,  E.  Newton. 

191 5      Studies  on  Light  Production  by  Luminous  Bacteria.     Amer.  Jour. 
Physiol.,  May,  191 5,  pp.  230-239. 

Henderson,  Lawrence  J. 

1913      The    Fitness   of   the   Environment.     Macmillan   Co.,   New   York, 

1913- 

Jepson,  Willis  Linn. 

191 1       A  Flora  of  Western  Middle  California.     Second  edition.     Cunning- 
ham, Curtiss  &  Welch,  San  Francisco,  191 1. 

Jordan,  Edwin  O. 

1908      A   Text-Book   of   General   Bacteriology.     W.   B.   Saunders,  Phila- 
delphia and  London,  1908. 

Kendall,  A.  1. 

191 5      The  Bacteria  of  the  Intestinal  Tract  of  Man.     Science,  August  13, 

1915,  pp.  209-212. 

Kohl,  F.  G. 

i903  Ueber  die  Organisation  und  Physiologic  der  Cyanophyceenzelle 
und  die  mitotische  Teilung  ihres  Kernes.  Gustav  Fischer,  Jena, 
1903. 

Lipman,  Charles  B. 

191 2  The  Distribution  and  Activities  of  Bacteria  in  Soils  of  the  Arid 
Region.  Univ.  Col.  Publ.  Agric.  Sciences,  October  15,  191 2,  pp. 
1-20. 

Minchin,  E.  A. 

1916  The  Evolution  of  the  Cell.  Amer.  Naturalist,  January,  1916,  pp. 
5-38;   February,  1916,  pp.  106-118;   May,  1916,  pp.  271-283. 


Moore,  F.  J. 

191 5      Outlines  of  Organic  Chemistry, 
and  London,  191 5. 


John  Wiley  &  Sons,  New  York 


OUve,  E.  W. 

1904      Mitotic  Division  of  the  Nuclei  of  the  Cyanophyceae. 
CentralbL,  Bd.  XVIII,  Abt.  I,  Heft  i,  1904. 


Beih.  Bot. 


300 


BIBLIOGRAPHY 


Osbom,  Henry  Fairfield. 

191 2  The  Continuous  Origin  of  Certain  Unit  Characters  as  Observed  by 
a  Palaeontologist.  Harvey  Soc.  Volume,  November,  191 2,  pp. 
153-204. 

Phillips,  O.  F. 

1904  A   Comparative   Study   of   the   Cytology   and   Movements   of   the 

Cyanophyceae.     Contrih.  Bot.  Lab.   Univ.  Penn.,  vol.  II,  no.  3, 
1904. 

Pirsson,  Louis  V.,  and  Schuchert,  Charles. 

191 5  A  Text-Book  of  Geology.  Part  I,  Physical  Geology,  by  Louis  V. 
Pirsson.  Part  II,  Historical  Geology,  by  Charles  Schuchert. 
John  Wiley  &  Sons,  New  York;   Chapman  &  Hall,  London,  191 5. 

Richards,  A. 

191 5  Recent  Studies  on  the  Biological  Effects  of  Radioactivity.  Science^ 
September  3,  191 5,  pp.  287-300. 

Rutherford,  Sir  Ernest. 

191 5      The  Constitution  of  Matter  and  the  Evolution  of  the  Elements. 

(1914)         First  series  of  lectures  on  the  William  Ellery  Hale  foundation, 

delivered  April,  1914.     Pop.  Sci.  Mon.,  August,  191 5,  pp.  105-142. 

Schuchert,  Charles. 

191 5      A  Text-Book  of  Geology  (with  Pirsson,  Louis  V.).     See  Pirsson. 

de  Vries,  Hugo 

1901       Die  Mutationstheorie.     Vol.  I.     Veit  &  Co.,  Leipsic,  1901. 
1903      Die  Mutationstheorie.     Vol.  IL     Veit  &  Co.,  Leipsic,  1903. 

1905  Species   and   Varieties,   Their   Origin   by   Mutation.     Open   Court 

Publ.  Co.,  Chicago;  Kegan  Paul,  Trench,  Triibner  &  Co.,  London, 
1905. 

Wager,  Harold. 

191 5  Behaviour  of  Plants  in  Response  to  the  Light.  Nature,  December 
23,  1915,  PP-  468-472. 

Walcott,  Charles  D. 

1 91 4  Cambrian  Geology  and  Palaeontology,  vol.  Ill,  no.  2,  Pre-Cambrian 

Algal  Flora.     Smithsonian  Misc.  Colls.,  vol.  64,  no.  2,  pp.  77-156, 
Washington,  1914. 

1915  Discovery  of  Algonkian  Bacteria.     Proc.  National  Acad.  Sci.,  April, 

1915,  pp.  256,  257. 


Wilson,  Edmund  B. 

1906      The  Cell  in  Development  and  Inheritance.     Second  edition, 
millan  Co.,  New  York,  1906. 


Mac- 


BIBLIOGRAPHY 


301 


CHAPTER  IV 
Calkins,  Gary  N. 

1916      General   Biology  of  the  Protozoan  Life  Cycle.     Amer.  Naturalist 
May,  1916,  pp.  257-270. 

Darwin,  Charles. 

1859      On  the  Origin  of  Species,  by  Means  of  Natural  Selection;    or  the 
Preservation  of  Favored  Races  in  the  Struggle  for  Life.     Murrav 
London,  1859.  ■^' 

Douglass,  Andrew  E. 

1914  The  Climatic  Factor  as  Illustrated  in  Arid  America  (with  Hunting- 

ton, Schuchert,  and  Kullmer).     See  Huntington. 

Heron-Allen,  Edward. 

1915  Contributions  to  the  Study  of  the  Bionomics  and  Reproductive 

Processes  of  the  Foraminifera.     Phil.  Trans.,  vol.  CCVI    B  320 
June  23,  1915,  pp.  227-279. 

Huntington^ EUswor^^^^  Schuchert,  Charles;    Douglass,  Andrew  E.,  and 

1914      The  Climatic  Factor  as  Illustrated  in  Arid  America.     Carnegie  In- 
stitution of  Washington,  Publ.  no.  192,  Washington,  1914. 
Hutchinson,  Henry  Brougham. 

1909  The  Effect  of  Partial  Sterilization  of  Soil  on  the  Production  of  Plant 
Food  (with  Russell,  Edward  John).  Introd.  and  part  I  See 
Russell. 

191 3  Ibid.,  part  II.     See  Russell. 
Jennings,  H.  S. 

1906      Behavior  of   the  Lower  Organisms.     Columbia   University   Press 
New  York,  1906.  ' 

1916      Heredity,  Variation  and  the  Results  of  Selection  in  the  Uniparental 
Reproduction  of  Difflugia  corona.     Genetics,  September,  1916   pp 
407-534- 
Kullmer,  Charles  J. 

1914  The  Climatic  Factor  as  Illustrated  in  Arid  America  (with  Hunting- 

ton, Schuchert,  and  Douglass).     See  Huntington. 

Loeb,  Jacques,  and  Wasteneys,  Hardolph. 

191 5  On   the  Identity  of  Heliotropism  in  Animals  and   Plants.     Proc. 

National  Acad.  Set.,  January,  191 5,  pp.  44-47. 

1915  The  Identity  of  Heliotropism  in  Animals  and  Plants.     Second  note 

Science,  February  26,  1915,  pp.  328-330. 
Minchin,  E.  A. 

1916  The  Evolution  of  the  Cell.     Amer.  Naturalist,  January,  1916,  pp. 

5-38;   February,  1916,  pp.  106-118;   May,  1916,  pp.  271-283. 


302 


BIBLIOGRAPHY 


Neumayr,  M. 

1889  Die  Stamme  des  Thierreiches.  Bd.  I,  Wirbellose  Thiere.  F.  Temp- 
sky,  Vienna  and  Prague,  1889. 

Osbom,  Henry  Fairfield. 

191 2  The  Continuous  Origin  of  Certain  Unit  Characters  as  Observed  by 

a   PahTontologist.     Harvey   Soc.    Volume,   November,    191 2,   pp. 
153-204. 

Pirsson,  Louis  V.,  and  Schuchert,  Charles. 

1915  A  Text-Book  of  Geology.  Part  I,  Physical  Geology,  by  Louis  V. 
Pirsson.  Part  II,  Historical  Geology,  by  Charles  Schuchert. 
John  Wiley  &  Sons,  New  York;  Chapman  &  Hall,  London,  191 5. 

Russell,  Henry  John,  and  Hutchinson,  Henry  Brougham. 

1909  The  Effect  of  Partial  Sterilization  of  Soil  on  the  Production  of  Plant 
Food.     Introd.  and  part  I.     Jour.  Agric.  Set.,  October,  1909,  pp. 

111-144. 

1913  Ibid.     Part  II.     Jour.  Agric.  Sci.,  March,  1913,  pp.  152-221. 

Schuchert,  Charles. 

1914  The  Climatic  Factor  as  Illustrated  in  Arid  America  (with  Hunting- 

ton, Douglass,  and  Kullmer).     See  Huntington. 

191 5  A  Text-Book  of  Geology  (with  Pirsson,  Louis  V.).     See  Pirsson. 

Waagen,  W. 

1869  Die  Formenreihe  des  Ammonites  suhradiatus,  Versuch  einer  palaon- 
tologischen  Monographic.  Geognostisch-palaontologische  Bei- 
trage,  herausgegeben  ...  von  Dr.  E.  W.  Benecke,  Bd.  II,  pp. 
179-257  (Heft  II,  S.  78).     R.  Oldenbourg,  Munich,  1869. 

Walcott,  Charles  D. 

1899  Pre-Cambrian  Fossiliferous  Formations.  Bull.  Geol.  Soc.  Amer., 
April  6,  189Q,  pp.  199-244. 

191 1  Cambrian  Geology  and  Palaeontology,  vol.  II,  no.  5.     Middle  Cam- 

brian Annelids.  Smithsonian  Misc.  Colls.,  vol.  57,  no.  5,  Septem- 
ber 4,  191 1,  pp.  109-144- 

191 2  Cambrian  Geology  and  Palaeontology,  vol.  II,  no.  6.     Middle  Cam- 

brian Branchiopoda,  Malacostraca,  Trilobita  and  Merostomata. 
Smithsonian  Misc.  Colls.,  vol.  57,  no.  6,  March  13,  191 2,  pp.  145" 
228. 

Wasteneys,  Hardolph. 

191 5      On  the  Identity  of  Heliotropism  in  Animals  and  Plants  (with  Loeb, 

Jacques).     See  Loeb. 
191 5      The  Identity  of  Heliotropism  in  Animals  and  Plants  (with  Loeb, 

Jacques).     Second  note.     See  Loeb. 


I 


BIBLIOGRAPHY 


303 


CHAPTER   V 
Abel,  O. 

191 2  Grundziige  der  Palaobiologie  der  Wirbeltiere.  E.  Schweizerbart'sche 
Verlagsbuchhandlung  Nagele  und  Dr.  Sproesser,  Stuttgart,  191 2. 

Dollo,  Louis. 

1895  Sur  la  Phylogenie  des  Dipneustes.  Bull.  Soc.  Beige  de  Ceol.,  de 
Paleontologic  ct  d'Hydrologie,  tome  IX,  1895,  Memoires,  pp.  79-128. 

1909  La  Paleontologic  ethnologique.     Biill.  Soc.  Beige  de  G60I.,  de  Paleon- 

tologic et  d'Hydrologie,  tome  XXIII,  1909,  Memoires,  pp.  377-421. 

Huxley,  T.  H. 

1880  On  the  Application  of  the  Laws  of  Evolution  to  the  Arrangement 
of  the  Vertebrata,  and  More  Particularly  of  the  Mammalia. 
Proc.  Zool.  Soc.  of  London,  1880,  pp.  649-662. 

Newcomb,  Simon. 

1902  Astronomy  for  Everybody.  McClure,  Phillips  &  Co.,  New  York, 
1902. 

Patten,  Wm, 

191 2  The  Evolution  of  the  Vertebrates  and  Their  Kin.  P.  Blakiston's 
Sons  &  Co.,  Philadelphia,  191 2. 

CHAPTER   VI 
Case,  £.  C. 

191 5  The  Permo-Carboniferous  Red  Beds  of  North  America  and  Their 
Vertebrate  Fauna.  Carnegie  Institution  of  Washington,  Publ. 
no.  207,  June  25,  1915. 

Dahlgren,  Ulric,  and  Silvester,  C.  F. 

1906  The  Electric  Organ  of  the  Stargazer,  Astroscopus  (Brevoort).  Ana- 
tomischcr  Anzeiger,  Bd.  XXIX,  no.  15,  1906,  pp.  387-403. 

Dahlgren,  Ulric. 

1910  The  Origin  of  the  Electricity  Tissues  in  Fishes.     Amer.  Naturalist, 

April,  iQio,  pp.  193-202. 
191 5      Structure  and  Polaritv  of  the  Electric  Motor  Nerve-Cell  in  To** 
pedocs.     Carnegie  Institution  of  Washington,  Publ.  no.  212,  191 5, 
pp.  213-256. 

Dean,  Bashford. 

1895  Fishes,  Living  and  Fossil.  Columbia  Univ.  Biol.  Ser.  Ill,  Macmil- 
lan  &  Co.,  New  York,  1895. 

Dohrn,  FeUx  Anton. 

1875  Der  Ursprung  der  Wirbelthiere  und  das  Prinzip  des  Funktions- 
wechsels.     Leipsic,  1875. 


304 


BIBLIOGRAPHY 


Klaatsch,  Hermann. 

1896  Die  Brustflosse  der  Crossoptcrygier.  Ein  Beitrag  zur  Anwcndung 
der  Archipterygium-Theorie  auf  die  Gliedmaassen  der  Landwir- 
belthiere.  Festschrift  zum  siebenzigstcn  Geburtstage  von  Carl 
Gegcnbaur,  Bd.  I,  1896,  pp.  259-392. 

Moody,  Roy  Lee. 

1916      The   Coal   Measures   Amphibia   of  North   America.     Carnegie  In 
stitution  of  Washington,  Publ.  no.  238,  September  28,  1916. 

Silvester,  C.  F. 

1906  The  Electric  Organ  of  the  Stargazer,  Astroscopiis  (with  Dahlgren, 
Ulric).     See  Dahlgren. 

Willey,  Arthur. 

1894  AmphioxHS  and  the  Ancestry  of  the  Vertebrates.  Columbia  Univ. 
Biol.  Ser.  II,  Macmillan  &  Co.,  New  York,  1894. 

WiUiston,  Samuel  W. 

191 1  American  Permian  Vertebrates.  University  of  Chicago  Press, 
Chicago,  191 1. 

Woodward,  A.  Smith. 

191 5  The  Use  of  Fossil  Fishes  in  Stratigraphical  Geology.  Proc.  Geol. 
Soc.  of  London,  vol.  LXXI,  part  i,  1915,  pp.  Ixii-lxxv. 


CHAPTER   VII 
Beebe,  C.  William. 

191 5      A  Tetrapteryx  Stage  in  the  Ancestry  of  Birds, 
ber,  191 5,  pp.  39-52. 


Zoologica,  Novem- 


DoUo,  Louis. 

1 901       Sur  I'origine  de  la  Tortue  Luth  (Dermochdys  coriacea).     Ext  rait  du 

Bull.  Soc.  roy.  des  sciences  med.  et  nat.  de  Bruxelles,   Februar>', 

1901,  pp.  1-26. 
Eochelone  hrabantica,  Tortue  marine  nouvelle  du  Bruxellien  (Eocene 

moyen)  de  la  Belgique.     Bull,  de  VAcad.  roy.  de  Belgique  (Classe 

des  sciences),  no.  8,  August,  IQ03,  pp.  792-801. 
Sur  TEvolution  des  Cheloniens  marins.     (Considerations  bionomi- 

ques  et  phylogeniques.)     Ibid.y  pp.  801-850. 
Les  dinosauriens  adaptes  a  la  vie   quadrupede  secondaire.     Bull. 

Soc.  Beige  de  Geol.,  de  Paleontologie  et  d'Hydrologie,  tome  XIX, 

1905,  Memoires,  pp.  441-448. 


1903 


1903 


1905 


Heilmann,  Gerhard. 

1913  Vor  Nuvaerende  Viden  om  Fuglenes  Afstamming.  Dunsk  Ornitlio- 
logisk  Forenings  Tidsskrift,  January,  191 5,  Aarg.  7,  H.  I,  II,  pp. 
1-71. 


BIBLIOGRAPHY 


305 


Lull,  Richard  Swann. 

1 91 5      Triassic  Life  of  the  Connecticut  Valley.     State  of  Connecticut  State 
Geol.  and  Nat.  Hist.  Survey,  Bull.  24,  191 5. 

Williston,  Samuel  W. 

1914      Water  Reptiles  of  the  Past  and  Present.     University  of  Chicago 
Press,  Chicago,  1914. 


CHAPTER  VIII 

Bacon,  Francis,  Lord  Bacon,  Baron  Verulam  and  Viscount  St.  Albans. 
1620      Novum  Organum.     English  version,  edited  by  Joseph  Devey,  M.  A. 
P.  F.  Collier  &  Son,  New  York,  191 1. 

Brown,  Amos  Peaslee. 

1909  The  Differentiation  and  Specificity  of  Corresponding  Proteins  and 

Other  Vital  Substances  in  Relation  to  Biological  Classification  and 
Organic  Evolution:  The  Crystallography  of  Hemoglobins  (with 
Reichert,  Edward  Tyson).     See  Reichert. 

Gushing,  Harvey. 

191 2  The  Pituitary  Body  and  its  Disorders,  Clinical  States  Produced  by 
Disorders  of  the  Hypophysis  Cerebri.  Harvey  Lecture,  1910, 
amplified.    J.  B.Lippincott  Co.,  Philadelphia  and  London,  191 2. 

DoUo,  Louis. 

1906  Le  pied  de  V Amphiproviverra  et  I'origine  arboricole  des  marsupiaux. 
Bull.  Soc.  Beige  de  Giol.,  de  Paleontologie  et  d'Hydrologie,  tome  XX, 
1906.     Proces  verbaux,  pp.  166-168. 

Gregory,  Wm.  K. 

1910  The  Orders  of  Mammals.     Bull.  Amer.  Mus.  Nat.  Hist.,  vol.  XXVII, 

February,  1910. 

Goodale,  H.  D. 

1916  Gonadectomy  in  Relation  to  the  Secondary  Sexual  Characters  of 

some  Domestic  Birds.  Carnegie  Institution  of  Washington, 
Publ.  no.  243,  Washington,  1916. 

Huxley,  Thomas  H. 

1893  Darwiniana  (vol.  II  of  Essays).  D.  Appleton  &  Co.,  New  York 
and  London,  1893. 

Lillie,  Frank  R. 

191 7  The  Free-Martin;   a  Study  of  the  Action  of  Sex  Hormones  in  the 

Foetal  Life  of  Cattle.  Jour.  Experimental  Zoology,  July  5,  191 7, 
PP-  371-452. 


3o6 


BIBLIOGRAPHY 


""tT  ptSog^al  Chemistry,  A  Text-BooU  and  Manual  for  Students. 
William  Wood  &  Co.,  New  York,  1916. 

"^t^T  ^-^e  and  Evolution.    Ann.  N.  Y.  Aca^.  Sciences,  vol.  XXIV. 
February  i8,  1915.  PP-  171-318. 

Osbom,  Henry  Fairfield. 

1897      Organic  Selection.    Science,  October  15,  1897,  PP-  583-587- 

1910      The  Age  of  Mammals  in  Europe,  Asia,  and  North  America.    Mac- 
millan  Co.,  New  York,  191°- 

Reichert,  Edward  Tyson,  and  Brown,  Amos  Peaslee. 

Thp  Differentiation  and  Specificity  of  Correspondmg  Proteins  and 

'^'      ^Ot?er"ta  Substances  in  Relation  to  Biological  Classification  and 

Organic  Evolution:   The  Crystallography  of  Hemogbbms.     Car- 

negieTnsUtution  of  Washington,  Publ.  no.  116,  Washmgton.  1909. 

^Zfo   %L  and  Function,   A  Contribution  to   the  History  of  Animal 
Morphology.    John  Murray,  London,  1916. 

Scott,  WilUam^B^^^  of  L.nd  Mammals  in  the  Western  Hemisphere.     Mac- 
millan  Co.,  New  York,  1913- 

APPENDIX 
""tea  The  ■  Dynamics   of   Living   Matter.     Columbia   University   Press, 

6      Th?OrIanfsm''as'a  Whole,   from  a  Physicochemical   Viewpoint^ 
X9:6      The  Organ^m^as  ^^^^^  ^^,  ^^.^^^^^^^^^^  p,,,,_  ^ew  York  and 

London,  1916. 

""tr  p1!ysioial  Chemistry,  A  Text-Book  and  Manual  for  Students. 
William  Wood  &  Co.,  New  York,  1910. 


INDEX 


Acadia,  134 

AcatUhaspis,  167 

Acceleration,  16,  17,  108,  145,  149,  233, 
252,  268,  279,  280 

Action  and  reaction,  5,  6,  12-23,  39,  53,  54, 
58,  68,  69,  71,  77,  80,  88,  98,  100,  106, 
no,  117,  118,  120,  142-145,  147,  150, 
152,  154,  160,  231,  242,  244-246,  271, 
279-283 

Adaptation,  7,  8,  10,  20,  23,  38,  46,  58,  143, 
144,  151-159,  174,  208,  225,  232,  236, 
239-249,  253-259,  262,  266,  273,  275, 
277,  281,  282;  see  Adaptive  radiation, 
Convergence,  Divergence,  Food  adapta- 
tions, Habitat  adaptations;  alternate, 
201,  203,  236,  240,  243;  convergent,  155 
(Fig.),  200  (Fig.),  207  (Fig.);  reversed, 
201,  203,  204,  236,  240,  241,  260 

Adaptive  radiation,  89,  114,  118,  119,  121, 
130,  131,  157-159,  168,  175,  180,  184, 
186,  189,  191-194,  201,  222,  227,  236- 
239,  259,  274 

Adirondacks,  100 

Adult,  106,  III,  147 

Africa,  82,  125,  183,  188,  194-196,  217,  225, 
236,  237,  241,  261,  263,  269;  see  South 

Agassiz,  Louis,  152 

Aglaspidae,  124 

Air,  18,  22,  33,  37,  45,  70,  84,  105,  106;  see 
Atmosphere 

Aistopoda,  178 

Alabama,  260 

Alaska,  206 

Alberta,  222,  223 

Algae,  32,  33,  38,  45,  49,  50,  53,  64,  66,  67, 
80,  90,  91,  99,  101-104,  105;  blue-green, 
loi,  102,  285,  286,  see  Cyanophyceae; 
earth-forming,  103;  limestone-forming, 
118,  137;  rock-forming,  103 

Algomian,  50,  153 

Algonkian,  50,  85,  86,  102-104,  120,  153, 
256 

Alligators,  186,  199 

Allosaurus,  213  (Fig.),  221. 


Alpine,  83 

Alps,  188,  255,  256 

Aluminum,  33,  34,  54 

Amalitzky,  W.,  191 

Amblypoda,  259 

America,  79,  164-166,  182,  190,  195,  237, 
255,  266;  see  North,  South 

Aminoacids,  86 

Amiskivia  sagiUiformis ,  129  (Fig.) 

Ammonia,  68,  83,  86 

Ammonites,  130,  137-139  (Fig.),  181,  213, 
291 

Ammonites  subradiatus,  138,  139  (Fig.) 

Ammonium  salts,  84,  85 

Ammonium  sulphate,  82 

Amwba,  57,  112,  116,  290;  Umax,  93  (Fig.); 
proteus,  112  (Fig.) 

Amphibamus,  178,  179  (Fig.) 

Amphibia,  131,  165,  172,  174,  177-183, 
185,  186,  196,  292;  see  Amphibians 

Amphibians,  161,  163,  175,  177-183,  185, 
190,  198-200,  210,  212,  231,  239,  246, 
253,  260,  275;  see  Amphibia 

Atnphioxiis,  162  (Fig.),  168,  292;  see  Lance- 
lets 

Anchisaitrus,  211  (Fig.),  213,  216  (Fig.) 

Angiosperms,  108 

Angiiilla,  174 

Animals,  40,  41,  51,  53,  55,  56,  69,  70,  80, 
91,  106-110,  285;  air-breathing,  166,  185; 
bipedal,  213,  216,  221,  224,  226,  227, 
229;  experiments  on,  74-79,  116,  117, 
247,  250,  251;  predaceous,  162,  169,  181, 
190,  234;  quadrupedal,  210,  216,  217, 
219,  220,  224 

Animikian,  50,  153 

Ankylosaiirus,  225 

Annulata,  118,  128  (Fig.),  130,  131,  291; 
see  Worms 

Anomodonts,  190,  191,  193 

Anomcepus,  211  (Fig.) 

Antarctic,  164,  166,  181,  185,  205 

Antarctica,  256 

Ant-eater,  259,  279;  spiny,  235  (Fig.) 

Antelopes,  225,  266,  292 


307 


3o8 


INDEX 


Antiarchi,  165-167  (Fig.) 

Antibodies,  73,  74 

Antillia,  206 

Anlilocapra,  266 

Antitoxin,  73,  74 

Anura,  178 

Apatosaimis,  213  (Fig.),  219,  220  (Fig.),  221 

Apes,  236,  237,  269,  274 

Aphroditidae,  128,  129 

Appalachian,  135,  136,  164,  181,  188,  256 

A  pus  lucasanus,  124  (Fig.) 

Arabella  opalina,  128  (Fig.) 

Arachnida,  125,  166;  see  Arachnids 

Arachnids,  130;  see  Arachnida 

Arccoscclis,  186  (Fig.) 

Archsean,  50,  100,  153,  256 

Archaeoceti,  241 

ArchcBopteryx,  227,  228-230  (Figs.),  292 

Archaeozoic,  34,  5o,  82,  95,  i53 
Archegosaurus,  182 
Archelon,  203  (Fig.),  206 
Arctic  Ocean,  206 
Arctic  seas,  134,  205 
Argentina,  217  , 

Argon,  41 
Arid,  185,  197 

Aridity,  107,  i35,  180,  254,  258 
Aristotle,  8,  9,  279 
Armadillo,  148,  224,  259 
Armature,  121, 132,  i53,  ^54, 161, 164-166, 
169, 179,  182, 187,  202,  203,  224,  225,  246 
Arrhenius,  Svante  A.,  49,  54 
Arsenic,  54  . 

Arthrodira,  166,  167   (Fig.),  292;  see  Ar- 

throdiran  fishes,  Arthrodires 
Arthrodiran  fishes,  172,  i75;  see  Arthro- 
dira, Arthrodires 
Arthrodires,  134,  168-170;  see  Arthrodira, 

Arthrodiran  fishes 
Arthropoda,  118,  130,  291;  see  Arthropods 
Arthropods,  124;  see  Arthropoda 
Articulates,  130,  132,  1 33 
Ascidians,  162,  168,  292 
Asia,  82,  237,  256,  261,  269,  274 
Aspidosaurus,  182 

Atmosphere,  9,  26,  28,  33,  34,  37,  39-42, 
43-45,  52,  68,  86,  87,  99,  106,  255;  see 
Air,  Carbon  dioxide.  Volcanoes 
Atomic  weight,  34,  55,  59,  67 
Atoms,  39,  54,  56,  59,  60,  97,  98,  n? 
Australia,  180,  203,  237,  255,  262 
Aye-aye,  150 
Azotobacter,  86,  87 


B 


Baboons,  239 
Bacon,  Francis,  12,  283 
Bacteria,  23,  31-33,  37,  38,  40,  42,  45,  48- 
51,  67,  80-93  (Fig.),  99,  ioi»  105,  iio» 
III,  143,   253,  254,   286;  see  Monads; 
aerobic,  87;  ammonifying,  84;  anaerobic, 
40,  42,  87,  89;  antiquity  of,  84,  85;  cal- 
careous, 104;  denitrifying,  85,  86,  91, 104; 
iron,  90,  118;  luminous,  91;  nitrifying, 
37,  62,  82-86,  no;  parasitic,  89;  proto- 
trophic, 81;  size  of,  81;  sulphur,  83,  90; 
symbiotic  relations  of,  82,  87,  89 

Bacterium  calcis,  90;  B.  radicicola,  87 

Bahama  Banks,  Great,  90 

Bain,  Andrew  Geddes,  189 

Balcrnoptcra  borealis,  234  (Fig.) 

Balance,  16,  17,  91,  i49,  233,  269,  280 

Baldwin,  J.  Mark,  244 

Baltic  Sea,  188 

Baptonodon,  205  (Fig.) 

Barathronus   diaphanus,    173    (Fig-),    i74 

(Fig.) 
Barbados,  115 
Barium,  33,  34,  36,  54,  66 
Barnacles,  113,  ^34,  291 
Barren,  Joseph,  62,  136,  213 
Barus,  Carl,  27 
Bateson,  William,  7,  ^45 
Bats,  236,  239,  259,  292 
Bears,  polar,  239 
Beaver,  239 
Bechhold,  Heinrich,  68 
Becker,  George  F.,  26,  35,  36,  4° 
Becquerel,  .\ntoine  Henri,  11 
Beebe,  C.  William,  228 
Belgium,  222 
Bcllina  danai,  121 
Bergson,  Henri,  10 
Bernissart,  222 

Bert,  Paul,  in 

Berthold,  77 

Berzelius,  Jons  Jakob,  57,  286,  287 

Beyjerinck,  83 

Bicarbonates,  42,  59 

Bighorn  Mountains,  160 

Big  Tree,  96 

Bion,  6 

Birds,  67,  131,  161,  211,  226-231,  232,  247, 
275,  292;  aquatic,  230,  231;  relation  ot 
plants  to,  105;  toothed,  227.  230,  292 

Birkenia,  165 

Bison,  225 


INDEX 


309 


Bivalves,  134,  136 

Black  Hills,  161,  218 

Blood,  15,  37,  63,  66,  72,  74,  79,  192,  232, 

247 
Body,    197,    207-209,    212,  219,  224-226, 
230-232,  239,  252,  261,  289,  290;  -cell, 
see  Cell;  -form,  163  (Fig.),  175,  179 

Bohemia,  177 

Bone,  10,  II,  64,  221,  226,  227,  265,  289 

Boron,  36,  54 

BoihriolcpiSy  165-167  (Fig.),  170 

Boveri,  Th.,  92,  94 

Bowfin,  168,  170,  292 

Brachiopoda,  131,  291;  see  Brachiopods, 
Lamp-shells 

Brachiopods,  65,  120,  121,  123  (Fig.),  130, 
134,  138,  171;  see  Brachiopoda,  Lamp- 
shells 

Brachiosaurus,  217,  219  (Fig.) 

Brachycephaly,  250 

Brachydactyly,  75,  76,  249,  250 

Brain,  63,  192,  214,  227,  232,  251,  259, 
289 

Branner,  J.  C,  83 

Brazil,  207 

British  Isles,  171 

Brogniart,  Alex,,  255 

Bromine,  33,  37,  54,  66 

Brontosaurus,  219,  220 

Brontotheriinae,  149 

Brontothcrinm,  263  (Fig.),  264,  270;  platy- 
ccras,  264  (Fig.) 

Broom,  Robert,  189 

Brown,  Amos  Peaslee,  79,  247 

Brown,  Barnum,  223 

Brown-Sequard,  Charles  Edward,  77 

Buflon,  Georges  Louis  Leclerc,  Comte  de, 
2,  253 

Bit  nodes,  154 

Biirgessia  beila,  124  (Fig.) 

Butschli,  O.,  67 


Cacops,  182  (Fig.) 

Calamoichthys,  174 

Calcareous,  alg£e,  103;  bacteria,  104;  ooze, 

198;  skeleton,  115 
Calcium,  33,  35-37,  46,  47,  54,  55,  63,  64, 

65,  67,  68,  71,  82,  84,  90,  246,  289 
California,  94,  96,  97 
Calkins,  Gary,  N.,  in 
Camarasaiiriis,  219  (Fig.) 


Cambrian,  28,  29,  38,  50, 102, 118, 122, 123, 
126-128, 131, 132, 134, 135, 152, 153, 161, 
168,  178,  193,  246,  256;  early,  123; 
Lower,  121;  mid-,  120,  121,  123,  129, 
130;  Middle,  118,  119;  post-,  153;  pre-, 
28,  50,  85,  90,  103,  117,  1x8,  120,  121, 
123,  130,  132,  134,  135,  152,  153,  246 

Camels,  262,  292 

Campbell,  William  Wallace,  3,  4 

Camptosaitriis,  221  (Fig.),  222 

Canada,  165,  223 

Canadia,  129;  spinosa,  128  (Fig.) 

Canon  City,  Colorado,  160,  161 

Capybara,  239 

Carbohydrates,  52,  58,  72,  87,  89,  loo,  248, 
280,  288 

Carbon,  9,  3^-33,  37,  4°,  4i,  4^,  47,  5^55, 
58,  62,  63,  67,  70,  82,  83,  86-88,  99-101; 
dio.xide,  40-42,  45,  52,  64,  68,  70-72,  82, 
86,  99,  285,  286 

Carbonaceous,  limestones,  32;  matter,  40; 
meteorites,  47;  shales,  32 

Carbonates,  54,  65,  90,  120,  246;  calcium, 
104,  153;  magnesium,  104 

Carbonic  acid,  9,  42,  59 

Carboniferous,  126,  135,  137,  153,  161,  168, 
169,  177-180,  193,   194,  211,  227,   236, 

256 
Camivora,     259;    see    Carnivores,    Food 

adaptations 
Carnivores,   236,  237,  258,  259,  292;  see 

Food  adaptations,  Carnivora 
Carnot,  N.  L.  Sadi,  12,  14 
Case,  E.  C,  180,  186 
Cassowaries,  230 
Catalysis,  54,  57,  58,  106,  150,  286,  287; 

see  Enzymes,  Berzelius  on,  57 
Catalyzer,  57,  58,  69,  72,  82,  116,  246,  280, 

287;  see  Enzymes 
Catfishes,  175 
Catskill  delta,  134 
Cattle,  225,  292 
Cell,  22,  68,  73,  78,  80,  82,  86,  88,  91-99, 

103,  114,  116,  286,  288,  289;  see  Germ; 

body-,  94,  98,  142-146,  150,  244,  253, 

283;  differentiation,  87,  93;  division,  61, 

116;  germ-,  77,  78,  94-96,  98,  105,  144; 

nucleus,  63,  73,  87,  92-94,  97,  102,  114, 

116;  wall,  87,  288 
Cellulose,  52,  loi 

Cenozoic,  135,  161,  168,  178,  193,  236 
Cephalaspis,  175 
Cephalopoda,  291;  see  Cephalopods 


3IO 


INDEX 


Cephalopods,  130,  181,  213;  see  Cepha- 
lopoda 

Ceratodtis,  172 

Ceratopsia,  224  (Fig.) 

Cetacean,  200,  236 

Chjetognatha,  129  (Fig.),  131,  291;  see 
Chaetognaths 

Chsetognaths,  120,  129;  see  Chaetognatha 

Chalk,  206 

Chalones,  74,  77,  78,  106,  150,  246,  280 

Chamaeleons,  239 

Chamberlin,  Thomas  Chrowder,  3,  25,  26, 

34 
Champsosanrns,  199  (Fig.) 

Characters,  4,  70,  9^,  io7,  "7,  I39,  142, 
145-152,  198,  207,  208,  233,  238-240, 
242,  244-246,  250-253,  258,  259,  263, 
265,  268,  270,  271,  275-278,  290 

Character  velocity,  107-109,  149,  150,  232, 
233,  252,  259,  265,  268,  279 

C  heir  acanthus,  170  (Fig.) 

CheirolepiSy  170  (Fig.) 

Cheiromys,  150 

Chelonia,  201-203 

Chemical,  compounds,  4,  17,  32,  35,  36, 
38,  45,  54,  56,  62,  70,  81;  elements,  4-6, 
14,  18,  19,  30,  31,  33-36,  45,  52,  54,  56, 
59;  evolution  of,  3;  messengers,  6,  15,  69, 
71-79,  88,  89,  98,  106,  107,  109, 150,  233, 
246,  251,  278,  279,  282,  283;  Huxley  on, 

57,72 

Chilonyx,  187 

Chitin,  132,  133,  153 

Chitinous,  armature,  121,  132,  165,  246; 
shield,  124 

Chlamydomonas,  113 

Chlamydoselache,  169 

Chlorine,  S3,  36,  37,  47,  54,  66,  82 

Chlorophyceae,  104 

Chlorophyll,  40-42,  48,  5i-53,  64,  65,  71, 
81,  99-101,  102,  118,  286 

Chlorophyllic  organs,  105 

Chordata,  153,  292;  see  Chordates 

Chordates,  50,  153,  161,  246,  292;  see 
Chordata 

Chromatin,  63,  78,  85, 91-99,  no,  116, 141- 
148,  154,  158,  231,  253,  263,  268;  body-, 
21,  77,  232,  253;  heredity-,  21-23,  77,  95, 
98,  99,  106-108,  no,  114,  116,  117,  142, 
143,  145,  147,  151,  177,  198,  199,  233, 
240-246,  251-253,  266,  278 

Chronology,  27-29,  36,  256 

Ciliata,  115;  see  Ciliate 


Ciliate,  112  (Fig.),  119,  290;  see  Ciliata 

Cirri  pedes,  134 

Cladoselache,  167  (Fig.),  168 

Clarke,  Frank  Wigglesworth,  3,  32,  36,  41, 

63,  68,  83,  103,  104 
Claws,  184,  215,  227 
Clepsydra  ps,  188 
Clidastes,  210 
Clostridium,  87 
Club-mosses,  180 
Coal,  135,  137 
Coal  measures,  177 
Coast  Range,  135,  218;  see  Pacific  Coast 

Range 
Cobalt,  54 

Coccosteus,  170  (Fig.) 
Ccelenterata,   118,   131,   290;  see   Ccelen- 

terate 
Ccelenterate,  113,  130;  see  Ccelenterata 
Cold,  49,  180,  254 

Colloids,  39,  54,  58,  59,  68,  84,  288,  289 
Colorado,  217,  220 
Comanchean,  153,  161,  168,  178,  193,  211, 

217,  218,  227,  236 
Combustion,  40,  52,  5 S»  61 
Comets,  47 

Compensation,  16,  158,  215,  280 
Competition,  21,  22,  69,  147,  188 
Condylar thra,  259 
Congo,  248 

Conifers,  108,  134,  212,  213 
Connecticut  valley,  210-213 
Continental,    depression,    135,    136;   seas, 
134,  198,  206,  210;  waters,  130 

Continents,  25,  26,  35,  36,  41,  181 

Continuity,  251,  276,  277 

Convergence,  154,  155,  i57,  165,  173 

Cooperation,  16,  69,  145,  240 

Coordination,  16,  69,  106,  145,  160,  240, 
246 

Cope,  Edward  Drinker,  143,  144,  i77,  186, 
188,  196,  216,  232,  237 

Copper,  36,  54,  66,  67,  71 

Corals,  103,  137,  213,  290 

Cordilleran  seas,  205 

Cordilleras,  122 

Correlation,  69,  106,  143,  240,  246,  280 

Coryphodon,  259  (Fig.) 

Corytfwsaurus,  223  (Fig.) 

Cotylosauria,  185,  191;  see  Cotylosaurs 

Cotylosaurs,    187,    190,   193;    see   Cotylo- 
sauria 

Coulter,  Merle,  108 


INDEX 


311 


Coutchiching,  50,  153 

Crab,  291;  see  Horseshoe  crab 

Credner,  Hermann,  177 

Cretaceous,  50,  194,  196-198,  205,  208-210, 
217-219,  221,  222,  224,  230,  255,  256, 
261;  lower,  135,  153,  161,  168,  178,  193, 
195,  211,  213,  217-219,  227,  236;  mid- 
dle, 224;  upper,  135,  137,  153,  161,  168, 
178,  193,  195-200,  203,  205,  206,  210, 
211,  213,  214,  222,  223,  227,  230,  236,  259 

Cricotus,  178,  181,  182  (Fig.),  200  (Fig.), 
210 

Crinoids,  66 

Crocodiles,  193,  194,  199-201,  211,  212, 
227,  231;  see  Crocodilia,  Crocodilian 

Crocodilia,  193,  196,  201,  210,  231;  see 
Crocodiles,  Crocodilian 

Crocodilian,  200,  292;  see  Crocodiles,  Croc- 
odilia 

Crossopterygia,  174,  186 

Crossopterygii,  168,  292;  see  ganoids,  lobe- 
finned 

Crustacea,  120,  121,  123,  131,  133,  134, 
291 ;  see  Crustacean 

Crustacean,  124,  125,  130;  see  Crustacea 

Cryptocleidus  oxonicnsis,  207  (Fig.) 

Cryptozoon  Ledge,  102 

Cryptozoon  proliferjim,  102  (Fig.) 

Cunningham,  J.  T.,  77,  78,  144 

Curie,  Pierre,  11 

Cuvier,  Baron  Georges  L.  C.  F.  D.,  24,  51, 
95,  196,  237,  240,  279 

Cyanophyceae,  92, 101,  103;  see  Alga?,  blue- 
green 

Cycads,  108,  212,  213 

Cyclostomata,  292;  see  Cyclostomes 

Cyclostomes,  168;  see  Cyclostomata 

Cymbospondyhis,  200  (Fig.),  205  (Fig.),  210, 
213 

Cynodonts,  190-192,  236 

Cynognathus,  190  (Fig.) 


Dactylometra  quinquccirra,  130  (Fig.) 

Dad  ox  yl  on,  134 

Dahlgren,  Ulric,  44 

Dakota,  222;  see  South 

Daphnia,  in,  113 

Darwin,  Charles,  2,  7,  8,  20,  23,  24,  27,  118, 

138,  140,  144,  145,  153,  157,  235,  240, 

250,  276 
Darwin,  Sir  George,  27 


Deer,  225,  292 

Defense,  17,  120,  131,  152,  160,  165,  187, 

202,  224,  225,  240,  260,  263 
Delta,  134,  189,  198,  262 
Democritus,  7,  8 
Dendrolagus,  203,  243 
Deperet,  Charles,  219 
Deposition,  65,  90 
Descartes,  Rene,  2 
Devonian,  50,  122,  123,  133-136,  138,  i53, 

161,  165-171,  175-178,  193,  256 
Diadectes,  187  (Fig.) 
Diatoms,  32,  33,  90,  104,  286 
Diddphys,  235  (Fig.) 

Differentiation,  23,  87,  93,  157,  249;  chem- 
ical, 78,  79 
Difflugia,  117 
Digestion,  61,  66,  280 
Digestive  organs,  129 
Digits,  206,  268 
Dimetrodon,  188,  189  (Fig.) 
Dingo,  247 

Dinichthys,  lys'jintermedius.  166  (Fig.),  167 
Dinocephalians,  190 
Dinoccras,  259 

Dinosauria,  210-225;  see  Dinosaurs 
Dinosaurs,  142, 186, 191,  193-197,  210-225, 
227,  229,  276,  292;  carnivorous,  210-216, 
224,   225;   "duck-bill,"    211,   222,   223; 
herbivorous,    216-225;    "ostrich,"    213- 
215  (Figs.);  "tyrant,"  224  (Fig.) 
Diplacanthiis,  167,  170  (Fig.) 
Diplocaidus,  179  (Fig.),  180  (Fig.),  182 
Diplodocus,  219  (Fig.),  221 
Dipnoi,  168, 170, 172,  292;  see  Fishes,  lung- 
Dipterus,  170  (Fig.) 
Divergence,  157,  270 
Dog,  247 

Dohm,  Felix  Anton,  246,  279 
DoHchocephaly,  250 
DoHchodactyly,  76,  249,  250 
Dollo,  Louis,  202,  209,  243 
Dolphin,  200,  204,  205,  230 
Driesch,  Hans,  10,  73 
Dromosaurs,  190 
Dugongs,  269 
Dynamics,  12;  see  Thermodynamics 


Earth,  4,  18,  22,  24-34,  39,  45,  52,  70,  80- 
84;  age  of,  25,  27-29;  crust,  61,  65,  90, 
118,  136;  evolution  of,  3,  7;  heat  of,  25- 


312 


INDEX 


27,  45,  48,  56,  84,  no;  stability  of,  25, 
34;  surface  of,  25-27,  30,  31,  33,  44,  45 

Echidna,  235  (Fig.) 

Echinodermata,  118,  130,  131,  291;  see 
Echinoderms 

Echinoderms,  66,  130,  171,  291;  see 
Echinodermata 

Edaphosaurus  cruciger,  188,  189  (Fig.) 

Edentates,  236,  237,  259 

Eel,  173,  176 

Egypt,  269 

Ehrenberg,  D.  C.  G.,  90 

Ehrlich,  Paul,  57,  247 

Elasmobranchii,  292;  see  Elasmobranchs 

Elasmobranchs,  168;  see  Elasmobranchii 

Elasmosaunis,  208  (Fig.) 

Eldonia  ludungi,  126,  127  (Fig.) 

Electric  organs,  176 

Electricity,  see  Energy,  electric,  of  elec- 
tricity 

Electrons,  59,  97,  98,  loi,  117 

Electroplaxes,  176 

Elements,  chemical,  4-6,  14,  18,  19,  30,  31, 
33-36,  45,  52,  54,  56,  59;  evolution  of,  3; 
life,  see  Life  elements;  metallic,  47,  48, 
54,  55,  64,  88;  non-metallic,  47,  54,  55, 
66,  88;  radioactive,  28,  56 

Elephant,  219,  261,  264,  269-273,  279,  292; 
see  Elephas 

Elephas,  269  (Fig.),  270;  see  Elephant; 
primigeninSy  271  (Fig).;  see  Mammoth, 
woolly 

Elimination,  99,  137,  220,  271;  see  Extinc- 
tion 

Elpidiidae,  126 

Embryo,  106,  108 

Embryonic  stages,  106,  108,  in 

Empedocles,  7,  8 

Endocrine  organs,  74 

Endothiodon,  190  (Fig.) 

Energy,  i,  3,  4,  10,  11,  17,  18,  20,  70,  91, 
95,  100,  105-107,  no,  III,  144,  145,  281; 
capture  of,  14,  16,  17,  48,  80,  87,  152; 
chemical,  14,  44,  113;  concept  of  life,  10- 
23,  281;  conservation  of,  12,  13,  15,  18, 
51,  53;  degradation  of,  11,  14,  53;  dis- 
sipation of ,  II,  14,  15;  electric,  39,48,  52, 
53j  55  >  see  Energy  of  electricity,  Ioniza- 
tion; four  complexes  of,  18-23,  98,  99, 
145,  147,  154;  kinetic,  13,  14,  21,  285; 
latent,  19,  278,  280;  life  a  new  form  of,  5, 
12;  life  due  to  an  unknown,  6,  12;  life- 
less, 48,  57;  living,  48,  51,  55;  mechan- 


ical, 14;  of  electricity,  12,  176;  see  En- 
ergy, electric;  Ionization;  of  gravitation, 
II,  12,  18;  of  heat,  12,  14,  53,  99,  100, 
113,  254,  280;  see  Cold;  Earth,  heat  of; 
Solar  heat;  Sun,  heat  of;  Temperature; 
Volcanic  heat;  of  life,  1 1 ;  of  light,  12,  43- 
45,  48,  49,  71,  99,  100,  loi,  113;  see 
Heliotropism,  Light,  Phosphorescence; 
of  motion,  10, 12, 14,  53,  280;  see  Motion, 
Newton's  laws  of;  Velocity;  of  radio- 
activity, 26;  of  reproduction,  18;  po- 
tential, 13,  15,  19,  21,  285;  physiochem- 
ical,  20,  22,  48,  58,  95,  99,  150;  radiant, 
II,  14,  41,  285;  release  of,  14,  17,  18,  55, 
61,  80,  152,  280,  285;  storage  of,  14,  16- 
18,  80,  87,  152,  280,  285;  transformation 
of,  II,  13-15.  17,  278-280 

England,  207 

Environment,  20,  70,  120,  135,  137,  142, 
143,  147,  177,  232,  238,  241,  247,  248, 
253-259,  271,  272,  275,  283;  inorganic, 
18,  21-23;  fo*^''  great  complexes  of,  18, 
25;  life,  19,  21-23, 82,  91 ,  98, 99, 105, 1 10, 
147,  154,  232,  233,  244,  253,  254,  278; 
lifeless,  no;  living,  145;  physical,  98, 
107,  145,  154,  159,  233,  244,  253,  254, 
278;  physicochemical,  147,  160,  232,  254; 
primordial,  24-42 

Enzymes,  15,  42,  57,  59,  69,  72,  73,  87-89, 
106,  116,  150,  246,  280,  287 

Eocene,  135,  200,  218,  236,  241,  255,  256, 
258-261,  263,  264,  268,  269,  274 

Eotitanops,  263  (Fig.),  264;  boreal  is,  264 
(Fig.);  gregoryi,  265 

Erosion,  26-28,  30,  32 

Eryops,  178, 180, 182  (Fig.),  183  (Fig.),  186, 
190 

Eucken,  Rudolf,  8 

Eiidendrium,  113 

Euglena,  113 

Eumicrerpdon,  179  (Fig.) 

Eurasia,  255 

Europe,  79,  82, 164-166,  180,  182, 183,  190, 
191,  194-196,  205,  206,  208,  209,  237, 
255,  256,  261,  262,  274 

Eurypterids,  121,  125,  132,  133  (Fig.),  137, 
154,  166,  291;  see  Sea-scorpions 

Eusarcus,  133  (Fig.) 

Evolution,  causes  of,  10,  20,  137,  245-251, 
253;  law  of,  10;  modes  of,  238-245,  251, 
252;  of  action  and  reaction,  16,  17;  of 
interaction,  16,  17;  of  life,  2,  3,  5,  11,  17, 
19;  of  matter,  lifeless  and  living,  3-7; 


INDEX 


313 


' 


of  the  earth,  3,  7;  of  the  elements,  3;  of 
the  foui  complexes  of  energy,  18;  of  the 
germ,  21,  23,  282,  283;  of  the  glands,  74, 
75;  of  the  psychic  powers,  114,  273;  of 
the  stars,  -5,  7;  theories  of,  Darwinian, 
114,  144-146;  Lamarckian,  xii,  78,  114, 
143-146;  telrakinetic,  22,  147;  tetra- 
plastic,  23,  147;  uniformitarian,  2,  24,  67 
Extinction,  167,  253,  270 


Faraday,  Michael,  56 
Fats,  58,  248,  280 
Feathers,  227,  228 
Ferns,  213;  see  Flora,  fern 
Fins,  129, 155-157, 164, 167-169, 172  (Fig.), 
174,  178,  181,  188,  199,  200,  204,  226, 
230  (Fig.) 
Fire-flies,  113 
Fischer,  Alfred,  91 

Fishes,  131,  i54,  i55,  i57,  160-176,  186, 
190,  199,  209,  210,  231,  239,  246,  253, 
260,  275,  292;  bony,  174,  175,  see  Tele- 
osts;    fringe-finned,    174,    see    Ganoids, 
fringe-finned;  lung-,  167,  168,  170  (Fig.), 
172,  174,  292,  see  Dipnoi;  pro-,  152,  161, 
162 
Flagellates,  in-113;  see  Mastigophora 
Flood-plain,  189,  196,  197,  217-220,  262 
Flora,  coal,  181,  185;  cycad-conifer,  181, 

185;  fern,  180,  see  Ferns;  lycopod,  180 
Fluorine,  33,  36,  54 

Food,  88,  89,  104,  III,  112,  114,  115,  120, 
136,  205,  230,  238-240,  250,  253,  254, 
257,  287;  adaptations,  carnivorous,  143, 
186,  188-192,  194,  238,  285;  herbivorous, 
143,  190-192,  211,  214,  238,  260,  285; 
insectivorous,  186,  192,  194,  235,  237, 
238;  omnivorous,  191,  285 
Foot,  149,  i59»  172  (Fig.),  182-184,  186, 

199,  212-214,  229,  236,  238,  240 
Foraminifera,  32  (Fig.),  33,  50»  io3,  iiS 

(Fig.),  137,  290 
Forests,  105;  hardwood,  217 
Form,  4,  10,  II,  17,  18,  20,  23,  51,  62,  80, 
95, 107,  114,  137,  138,  142-145,  151, 152, 
157,  160,  163,  165,  231,  235,  240,  247, 
252,  258,  280 
Fox,  247 

Fraas,  Eberhard,  200 
France,  217,  219,  263 
Fresh- water,  life,  35,  38,  42;  plants,  63 


Freundlich,  59 

Fritsch  (Fric),  Anton,  177 

Frog,  177,  178,  292 

Function,  4,  10,  16,  19,  20,  46,  53,  55,  61, 
62,  69,  70,  87,  107,  114,  115,  119,  142- 
145,  151,  154,  157,  160,  198,  231,  235, 
239,  244-246,  2^2,  258,  280 

Fungi,  67 


Galeopithecus,  239 

Ganoids,  168-170  (Fig.),  175,  190,  292; 
fringe-finned,  178,  see  Fishes,  fringe- 
finned;  lobe-finned,  168,  170,  292,  see 
Crossopterygii 

Garpike,  168,  170,  292 

Gaspe,  171 

Gastropoda,  291;  see  Gastropods 

Gastropods,  120,  130;  see  Gastropoda 

Gastrostomus  hairdi,  173  (Fig.),  174  (Fig.) 

Gaudry,  Albert,  257 

Gavials,  199,  211 

Gegenbaur,  Carl,  169,  172 

Geikie,  Archibald,  29 

"General  Sherman,"  96,  98 

Geosaunis,  200  (Fig.),  210 

Germ,  49,  144,  i47,  150,  282,  283;  see  Cell; 
heredity-,  n,  19,  20,  280,  283;  life-,  12 

Germany,  172,  217 

Gies,  W.  J.,  32,  35,  38,  52,  61-63,  72 

Gigantactis    ranhoefeni,    173    (Fig.),    174 

(Fig.) 

Gigatiiosaurus,  217,  219 

Gigantura  chuni,  173  (Fig.),  174  (Fig.) 

Gila  monster,  187 

Gills,  178 

Giraffe,  248  (Fig.),  249,  279,  292 

Glacial  conditions,  185 

Glacial  Epoch,  254,  271 

Glaciation,  135,  180,  270,  271 

Glacier,  102 

Glands,  74-77,  246,  251;  see  Internal  Se- 
cretion; pineal,  75;  reproductive,  283, 
289;  sex,  75 

Globigerina,  32  (Fig.);  bulloides,  115  (Fig.) 

Glossopteris,  180 

Glucose,  287,  289 

Glycogen,  58 

Glyptodon,  148  (Fig.) 

Gneiss,  28 

Gondwana,  125,  171,  180,  217 

Gorganopsians,  190,  191 


INDEX 


Gorilla,  239 

Graham,  Thomas,  68 

Granite,  26,  30,  32 

Graphite,  32,  47,  118,  153 

Gravitation,  see  Energy  of  gravitation 

Gravity,  68;  see  Energy  of  gravitation 

Great  Bahama  Banks,  90 

Great  Britain,  217 

Great  Plains,  213,  262 

Gregory,  W.  K.,  149,  235 

Grenville,  50,  100,  103,  104,  153 

Greyson  shales,  120 

Growth,  16,  61,  75,  142,  144,  147 

Gymnosperms,  108 

Gymnotus,  174,  176 


Habitat,   adaptations,   iS5-i59,  257,  am- 
bulatory, 216,  burrowing,  120,  126,  128, 
climbing,   227,   239,  243,  cursorial,  190, 
212,    227,   229,    243,    259,  266,  digging, 
239,  flying,  199,  226-230,  239,  gravipor- 
tal,  259,   263,  leaping,   239,  parachute, 
227,  running,  239,  saltatorial,  243,  swim- 
ming, 127,  128,  142,  143,  161,  162,  187, 
199,  230,  231,  260,  volplaning,  239;  ma- 
rine, 195,  198,  200-202,  205,  260;  zones, 
152,    157-159,    i79»    199,    236,  238-241, 
254,  257,  aerial,  130,  131,  133,  156,  157, 
194,  227,  239,  aero-arboreal,  239,  aquatic, 
179,  187,  198-210, 227, 230, 241,  260,  270, 
abyssal,    120,    131,   156,   i73-i75»   239, 
deep-sea,  120,  194,  fluviatile,  131,  156, 
194-196,  198-202,  239,  270,  lacustrine, 
156,  littoral,  119,  131,  156,  162,  174,  186, 
199-202,  239,  270,  paludal,  201,  palus- 
tral,  156, 179,  200,  pelagic,  115, 119, 120, 
122,   126,  127,  131,  156,  200-210,  239, 
arboreal,  130,  131,  156,  203,  227,  229, 
230,   235-239,   241,   243,   244,   arboreo- 
terrestrial,  227,  236,  239,  243,  fossorial, 
126,  131,  156,  179,  239,  terrestrial,  130- 
133,   136,   156,   179,   186-188,   194-196, 
198-204,  210,  211,  227,  229,  230,  239, 
241,  243,  244,  258,  260,  270,  terrestrio- 
aquatic,  194,  202,  239 

Haeckel,  Ernst,  152 

Hair,  147,  290 

Hale,  George  Ellery,  47 

Halimedaj  103,  104 

Halley,  Edmund,  35 

Hamilton,  134,  136,  138 


Hand,  149,  150  (Fig.),  184,  215,  iso,  251 

Hartleb,  R.,  83 

Head,  129, 183, 187,  190,  208,  209,  222-226, 

252,  259,  279 
Heart,  192 

Heat,  see  Energy  of  heat 
Heliotropism,  52,  iii,  113 
Helium,  41 

von  Helmholtz,  H.  L.  F.,  12,  13,  53 
Hemocyanine,  66 
Hemoglobin,  67,  247 
Henderson,  Lawrence  J.,  9,  20,  70 
Heraeus,  82 

Herbivora,  263,  265,  266;  see  Food  adapta- 
tions, herbivorous;  Herbivore 
Herbivore,    263;    see    Food    adaptations, 

herbivorous;  Herbivora 
Heredity,  10,  16,  19,  63,  77,  78,  93,  94,  98, 
146,  147,  239,  281,  282,  289;  see  Chro- 
matin, heredity-;  Germ,  heredity- 
Hertwig,  Gunther,  94 
Hertwig,  Oskar,  94 
Hertwig,  Paula,  94 
Hesperornis,  230  (Fig.) 
Himalayas,  255,  256,  274 
Hip  par  ion,  266,  267  (Fig.) 
Hipf)opotamus,  239,  292 
Hitchcock,  Edward,  210 
Hoatzins,  227 
Iloloptychius,  170  (Fig.) 
Holothurian,  126,  127;  see  Holothuroidea, 

Sea- cue  umbers 
Holothuroidea,  125,  291;  see  Holothurian, 

Sea-cucumbers 
Hoppe-Seyler,  51 
Hormones,  5,  74,  77,  78,  106,  116,  150,  246, 

280 
Horns,  149,  224,  260,  264  (Fig.),  265 
Horse,  151,  159,  258  (Fig.),  260,  262,  263, 

266-268  (Figs.),  292 
Horseshoe  crab,  124  (Fig.),  125,  132,  291 
Hot  springs,  102,  103 
Howe,  Marshall  A.,  67,  104,  105 
von  Huene,  Friedrich,  221 
Humidity,  135,  180,  258 
Huntington,  Ellsworth,  136 
Hiippe,  82 
Huronian,  50,  153 
Hutton,  James,  24 
Huxley,  Thomas,  28,  57,  72,  191,  194,  235, 

237,  240,  241,  25s,  274 
Hycenodotij  241 
Hyatt,  Alpheus,  108,  152 


INDEX 


315 


Hydrocarbons,  71 

Hydrogen,  9,  31,  33,  38-40,  46,  47,  49,  Si" 

55,  58,  59-61,  63,  66,  67,  70-72,  88,  97, 

98,  100,  lOI 
Hydroid,  113,  290 
Hydrosphere,  26,  33,  34,  99 
Hypohippus,  266,  267  (Fig.) 


IcfUhyornis,  230 

Ichthyosauria,  201;  see  Ichthyosaurs 
Ichthyosaurs,  155  (Fig.),  172,  193-196,  200, 
203-205  (Figs.),  207,  210,  213,  230,  239, 
292;  see  Ichthyosauria 
IctidopsiSy  190  (Fig.) 
Iguanodontia,   221-223,   224;  see  Iguano- 

donts 
Iguanodonts,  197,  211,  221-223;  see  Igua- 
nodontia 
Immunity,  73,  74 
India,  180 
Indian  Ocean,  201 

Individual,  19,  20,  22,  23,  68,  69,  78,  92,  95, 
97,  103,  144,  147,  154,  233,  238,  244,  249 
Individuality,  113,  148 
Inhibition,  65,  66,  74 

Inorganic,  compounds,  107,  143;  environ- 
ment, see  Environment,  inorganic 
Insccta,  133,  253,  291;  see  Insects 
Insectivore,   235-237,   239,  259,  292;    see 

Food  adaptations 
Insects,  130,  136,  181,  185,  254,  291;   see 

Insecta;  relation  of  plants  to,  105 
Interaction,  5,  6,  15-23,  39,  53,  54,  56-58, 
68,  69,  71-79,  80,  98,  106,  109,  116-118, 
120,  142-145,  147,  150,  152,  154,  160, 
231,  233,  242,  244-246,  251,  268,  271, 
278,  280,  282,  283 
Internal  secretion,  74-79,   ^43,   160,  249- 

251,  280,  282,  288,  289 
Invertebrata,  1 18-140,  146,  153,  i54,  253; 

see  Invertebrates 
Invertebrates,  33,  50,  64-66,  75,  117,  "8- 

140,  153,  160,  231;   see  Invertebrata 
Iodine,  54,  66 

Ionization,  39,  53-56,  63,  66;  see  Ions 
Ions,  14,  39,  54-56,  59,  61,  63,  67,  97,  117, 
see  Ionization;   negative,  54,  55,  66,  88, 
176;  positive,  54,  55,  88,  176 
Iron,  32,  2>3>,  46,  47,  50,  52,  54,  65,  66,  67, 

68,  71,  82,  88,90,  118,  153 
Italy,  206 


Jaekel,  Otto,  217 

James,  William,  7 

Jaws,  190,  191,  214,  230,  24s 

Jellyfish,  126,  127,  129,  130  (Fig.),  290 

Jennings,  H.  S.,  113,  115-117 

Johannsen,  W.,  147 

Joly,  28,  36 

Joule,  James  Prescott,  13 

Jurassic,  135,  138,  153,  161,  168,  175,  178, 
193-196, 198, 200, 205, 207, 210, 211, 213, 
217,  221,  222,  224,  227-230,  236,  256 


Kangaroo,  239,  243,  244,  292;    tree,  203, 

239,  243,  244 
Kansas,  209 
Kant,  Emmanuel,  2 
Karoo,  189 
Keewatin,  50,  153 
Kelvin,  William  Thomson,  Lord,  14,  27,  49, 

53 
Keratin,  63,  153 

Keweenawan,  50,  153 

King,  Clarence,  27 

Kligler,  Israel  J.,  87,  89,  91 

Kohl,  F.  G.,  92 

KoUiker,  A.,  94 

Kowalevsky,  Woldcmar,  257,  266 

Krakatau,  285,  286 

Kritosaur,  222;  see  Kritosaurus 

Kritosaiirus,  223  (Fig.);  see  Kritosaur 

Krypton,  41 


Labidosaiirus,  187  (Fig.) 

Labyrinthodont,  183 

Lacertilia,  193,  201,  231;  see  Lizards 

Lagoons,  184,  189,  196-198,  220,  262 

de  Lamarck,  Jean  Baptiste  P.  A.  de  Monet, 

2,  143,  157,  232,  249,  253,  279 
Lampreys,  168 
Lamp-shells,   122,   123,   291;    see  Brachi- 

opoda,  Brachiopods 
Lanarkia,  165 

Lancelets,  162  (Fig.),  292;  see  Amphioxus 
Laplace,  Pierre  Simon,  Marquis  de,  25,  34, 

286 
de  Lapparent,  Albert  A.  C,  29 
Laramide,  135,  136 


3i6 


INDEX 


Lariosaurus,  206,  207  (Fig.) 

Laurentian,  50,  153 

Lavoisier,  Antoine  Laurent,  2,  51,  286 

Lead,  54 

Leatherbacks,  202  (Fig.),  203 

Leidy,  Joseph,  196,  237 

Lemur,  150,  236,  237,  239,  261,  274 

Leopards,  225 

Lepidosireriy  174 

Lias,  50 

Lichens,  32 

Life,  2,  4-6,  II,  12,  15,  145,  281,  286,  288; 
bacterial  stages  of,  70,  80;  dependent  on 
temperature,  48-50;  elements,  6,  33,  34, 
37-39,  45-48,  53-56,  5«r7i,  82;   energy 
concept   of,    10-23,    281;    environment, 
see  Environment,  life;    first  appearance 
of,  4;  evolution  of,  2,  3,  5,  11,  17,  i9,  98, 
99;  latent,  48;  orderly  processes  of,  116, 
288;  origin  of,  i,  2,  10,  20,  23,  35,  38,  41, 
43,  49,  50,  58,  67,  80,  81,  145;   primary 
stages  of,  67-71;  subject  to  chance,  7-9, 
146;   subject  to  law,  7-9,  146;   theories 
of,  creation,  5,  entelechy,  10,  277,  mate- 
rialistic, 3,  6,  mechanistic,  2,  6,  vitalism, 
2,  10,  52,  vitalistic,  2,  6,  10 
Light,  see  Energy  of  Ught;  production,  9, 
see   Phosphorescence;     ultra-violet,   60, 
84;  velocity  of,  11 
Limb  bones,  168,  265,  266 
Limbs,  155,  168,  172,  174,  178,  182-184, 
186, 187, 190, 192, 197, 198,  200,  204,  206, 
208,   209,   213-216,   219,   224,   227-229, 
238-240,  252,  257,  265,  266,  269,  270 
Lime,  50,  91,  102,  120,  246 
Limestone,  32,  65,  83,  85,  86,  90,  103,  104, 

118,  135,  137,  153 
LimnosceliSj  187 
Limulus,  125,  132;  Polyphemus,  124  (Fig.), 

125 
Lingula,  121;  analina,  122,  123  (Fig.) 
Lingulella,   121-123;  acuminatay   121,   123 

(Fig.) 
Linnaeus,  234 
Lions,  225 
Lists,  see  Tables 
Lithium,  54 
Lithosphere,  26,  33,  34 
Lithothamnium,  103 
Lizards,  186,  188,  193,  194,  201,  231,  239, 

292;  see  Lacertilia;   half-,  206;   sea,  209 

(Fig.),  210 
Lockyer,  Sir  Joseph  Norman,  3 


Locomotion,  17,  112,  115,  120,  131,  152, 
154-157, 159, 165,  212,  224,  227,  229,  239 
Loeb,  Jacques,  42,  64,  66,  iii 
Loeb,  Leo,  78 
Loons,  230 
Loricaria,  175 

Louisella  pedunculata,  126,  127  (Fig.) 
Lull,  R.  S.,  216,  219 
Lungs,  66,  178 
Lyell,  Charles,  24,  103,  254 
Lysorophus,  181 


M 


Macaques,  239 

Mackenzia  costalis,  126,  127  (Fig.) 

Madagascar,  150 

Magnesium,  33,  36,  37,  46,  51,  54,  5S»  63, 

64,  65,  67,  68,  71,  82,  84,  loi 
Malayan  Peninsula,  261 
Mammalia,   190,   191,  234-274,   292;    see 

Mammals 
Mammals,  23,  126,  131,  137,  ^^42,  i49,  i55» 

161, 163, 165, 190-193, 198,  200,  231,  232, 

234-274,  275;    see  Mammalia;    clawed, 

236,  239;  egg-laying,  236,  237,  292,  see 
Monotremata,  Monotremes;  hoofed,  236, 

237,  258,  259;    pouched,  236,  237,  292, 
see  Marsupialia,  Marsupials;  pro-,  192 

Mammoth,  woolly,  271  (Fig.),  273 
Man,  46,  236-238,  269,  273  (Fig.),  274,  281 
Manatees,  236,  237,  239,  269,  270 
Manganese,  33,  52,  54,  7i,  82,  88,  loi 
Manieoceras  mantcoceras,  264  (Fig.) 
Marine,  habitat,  see  Habitat,  marine;  life, 

37,  38,  42;   organisms,  66;    plants,  63 
Marsh,  Othniel  C,  196,  216,  230,  237 
Marsupialia,  237;  see  Mammals,  ix)uched; 

Marsupials 
Marsupials,  203,  235,  236,  243,  292;    see 

Mammals,  pouched;  Marsupialia 
Mastigophora,  112   (Fig.),  115,  290;    see 

Flagellates 
Mastodons,  261,  264,  270,  273,  292 
Matter,  i,  4,  10,  12,  18,  46,  51,  58,  68,  70, 

95,  145;   living,  64,  67,  286-288 
Matthew,  W.  D.,  235,  257 
Mediterranean,  171,  188,  217,  260 
Medusa,  126,  130 
Melanostomias  mclanops,   173    (Fig.),   174 

(Fig.) 
Merostomata,  121,  166;  see  Merostomes 
Merostomes,  124,  130;  see  Merostomata 


INDEX 


317 


Mesohippus,  266  (Fig.) 
Mesosaurus,  207  (Fig.) 
Mesozoic,  135,  153,  161,  168,  178,  193.  ^94, 

200,  206,  208,  236,  254,  255 
Metazoa,  94;   see  Organisms,  many-celled, 

multicellular 
Metchnikoff,  E.,  276 
Meteorites,  30,  47,  49 
M  do  pi  as,  183 
Meuse,  River,  209 
Mexico,  206 

von  Meyer,  Hermann,  177 
Mice,  79,  271 
Micrococcus,  85 
Migration,  106, 114, 136, 154, 158, 180,  202, 

205,  254,  255,  257,  261,  262 
Minchin,  E.  A.,  92 
Mmer,  Roy  W.,  120,  123 
Miocene,  135,  236,  255,  256,  261,  267 
Mississippi  Sea,  134 

Mississippian,  153,  161,  168,  178,  193,  227 
Mites,  133,  291 

Molaria,  125;  spinifcra,  124  (Fig.) 
Molecules,  39,  54-56,  58,  87,  97,  99,  loi, 

117 
Moles,  239 

Mollusca,  90,  118,  131,  291;  see  Molluscs 
Molluscoida,  118,  291 
Molluscs,  66,  130,  137;   sec  Mollusca 
Monads,  17,  23,  46;  see  Bacteria 
Monkeys,  236,  237,  269,  274 
Monodactylism,  159 

Monotremata,    237;    see   Mammals,   egg- 
laying;  Monotremes 
Monotremes,  235,  236,  292;  see  Mammals, 

egg-laying;  Monotremata 
Montana,  86,  102,  214,  222 
Moodie,  Roy  L.,  177,  180 
Moon,  27,  29,  30  (Fig.),  44 
Morgan,  Lloyd,  244 
Mormyrus,  176 
Morrison,  218,  220;  formation,  217;  time, 

219 
Mosasauria,  201,  209;  see  Mosasaurs 
Mosasaurs,  186,  193,  195,  196,  200,  206, 

208-210,  226,  239,  292;  see  Mosasauria 
Mosasaunis,  209 

Motion,  160,  162,  184,  225;  see  Energy  of 
motion;    Newton's  laws  of,  12,  13,  18, 

22,53 
Moulton,  F.  R.,  34 
Mountain,    formation,     134;     revolution, 

135  (Fig.),  256  (Fig.);  upheaval,  136 


Mountains,  181,  206,  255 

Mount  Stephen,  B.  C,  122 

Miintz,  A.,  83 

Muridae,  271 

Muscle,  10,  II,  162,  176,  289 

Mutation,  63,  117,  138,  146;   of  de  Vries, 

106,   107,   140,   145,   268;    of  Waagen, 

138-140  (Figs.) 
Mutationsrichtung,  138,  140,  242 


N 


Nageli,  C,  93 

NcLosaurtis,  221 

Nathanson,  83 

Nautilus,  138,  291 

Neck,  208,  209,  225,  248-250,  270,  279 

Nemichthys    scolopaceus,    173    (Fig.),    174 

(Fig.) 
Neolcniis  serratus,  121  (Fig.) 
Neon,  41 
Neoscopelus  macrolepidotus,  173  (Fig.),  174 

(Fig.) 

Nereis  virens,  128  (Fig.) 

Nerves,  63,  176 

Nervous  system,  106, 107, 143, 184,  232,  280 

Neumayr,  M.,  242 

Nevada,  205 

Newark  time,  210-212 

New  Brunswick,  171 

Newcomb,  Simon,  141 

New  Guinea,  237,  273 

New  Jersey,  222 

New  Zealand,  208 

Newland  limestone,  85,  86 

Ncwlandia  conccntrica,  102  (Fig.);  N. /ron- 
dos a,  102  (Fig.) 

Newt,  178,  292 

Newton,  Sir  Isaac,  2,  12-14,  18,  22,  53 

Nickel,  54 

Nile,  269 

Niton,  41 

Nitrate,  38,  45,  54,  62,  68,  82,  83,  86,  91, 
105,  285 

Nitrite,  38,  68,  82,  84,  86 

Nitrobacler,  82,  83,  86 

Nitrogen,  31,  2>i,  37,  38,  40,  41,  46,  47,  51, 
54,  58,  62,  63,  67,  68,  70,  81-88,  91,  99, 
loi,  104,  105,  286 

Nitroso  coccus,  85,  86;  N.  monas,  82,  86 

Noctiluca,  116 

North  America,  134, 136, 148, 164, 175, 180, 
183, 184, 189, 191. 194-196, 198, 203, 205, 


3i8 


INDEX 


206, 208, 210, 212, 217, 219, 237, 25s,  256, 
259,  261-263,  266,  270,  274 

Nostocaceae,  286 
Nothosaurs,  201,  239 
Nuclein,  92,  95 
Nucleoproteins,  116 
Nutrition,  16,  143,  280,  289 

O 

Ocean,  4,  27,  38,  41,  80,  134;  age  of,  35,  36; 

salt  in  the,  29,  35-37 
Oceanic,  basins,  25,  26,  118;  invasion,  135, 

136 
Offense,  17,  120,  131,  152,  160,  165,  224, 

225,  240,  263 
Ohio,  166,  167,  177 
Okapi,  248  (Fig.),  268 
Old  Red  Sandstone,  170 
OlenelluSy  121 
Oligocene,  135,  236,  255,  256,  261-264,  266, 

267,  269,  274 
Olive,  E.  W.,  92 
Ontogeny,  108,  149 
Ooze,  T,2  (Fig.);  calcareous,  198;  siliceous, 

104 
Ophiacodon,  186 

Ophidia,  193,  201,  231;  see  Snakes 
Opisthoprocius    solcatns,    173    (Fig.),    174 

(Fig.) 
Opossum,  235  (Fig.),  236,  237,  243,  292 
Ordovician,  50, 122, 123, 134,  i35,  i53>  160- 
162,  165,  168,  178,  193,  256 

Organic,  compounds,  56,  58,  60,  67,  69-71, 
loi;  deposits,  32,  33 

Organism,  14-23,  39.  53 »  56-59»  68-72,  78, 
97,  99,  114,  14s,  152,  238,  241,  246,  281- 
283,  286;  many-celled,  69,  no,  117,  245, 
see  Metazoa;  multicellular,  91,  94,  99, 
103,  116,  see  Metazoa;  single-celled,  69, 
no,  112,  117,  118,  245,  see  Protozoa; 
unicellular,  91,  94,  102,  no,  115,  see 
Protozoa 

Omithischia,  210,  221,  224 

OrnilholesteSy  213 

Ornithomimus,  213-215 

Orohippus,  258  (Fig.) 

Osteolepis,  170  (Fig.) 

Ostracodermata,  292;  see  Ostracoderms 

Ostracoderms,    154,    161,    164-170   (Fig.); 
see  Ostracodermata 

Ostriches,  229,  230,  292 

Otters,  239 


Owen,  Richard,  177,  189,  196,  237 
Oxidation,  53,  60,  61,  90,  91,  100,  280 
Oxygen,  9,  33,  37-42,  46,  47,  51-56,  61,  62. 

63,  66,  67,  70,  71,  82,  86-91,  99,  loi 
Oxyhemoglobin,  66,  79,  247 


Pacific,  122;  Coast,  206,  213;  Coast  Range, 

136;  see  Coast  Range 
Paddle,  172  (Fig.),  187,  200,  204,  206-209, 

230 
Pdaaspis,  165  (Fig.) 
Palaeocene,  236,  259,  261 
Palceamastodon,  269  (Fig.),  270 
Palaeozoic,  28,  29,  34,  5o»  I04,  120,  135,  153, 
160,  161,  168,  175,  178,  181,  193,  200, 
236,  2S4,  255;  post-,  28;  pre-,  28,  29,  85 
Palisade,  256 
Palm,  sago,  108 
Palmyra  aiirijera,  129 
Pancreas,  76,  289 
Panlolamhda,  259  (Fig.) 
Pantylus,  187 
Paradoxidcs,  125 

Parasitic,  bacteria,  89;  plants,  105 
Parasuchia,  201 
Parathyroid,  75,  250,  289 
Pareiasauria,  185,  191;  see  Pareiasaurs 
Pareiasaurs,  190,  191;  see  Pareiasauria 
Paris,  255 
Pasteur,  Louis,  89 
Patagonia,  219 
Patriocdis,  241 
Patten,  William,  154 
Pclagothnria  nalatrix,  127  (Fig.) 
Pelvis,  210,  221,  223 
Pelycosaur,  186,  193 
Pelycypoda,  291;  see  Pel ycy pods 
Pelycyixxis,  130;  see  Pelycypoda 
Penguin,  230  (Fig.) 
Pennsylvania,  176,  177,  180 
Pennsylvanian,  153, 161, 168, 178, 193,  211, 

227 

Pentacta  frondosa,  126,  127  (Fig.) 

Permian,  122,  135,  153,  161,  168,  178-186, 

188-191,   193,   194,   198,   207,   210-212, 

226,  227,  236,  237,  255,  256;  reptiles,  201 

Permo-Carboniferous,  182,  186,  187,  190, 

210 
Permo-Triassic,  135,  189 
Peytoia  nathorsti,  129,  130  (Fig.) 
Phalanger,  239,  243 


INDEX 


319 


Pheasant,  228  (Fig.) 

Phillips,  John,  28,  29,  53 

Phillips,  O.  P.,  92 

Phosphate,  65,  71,  120,  246,  285;  calcium, 

153 
Phosphorescence,   14,  56,  113;    see  Light 

production 

Phosphorescent  organs,  173-176 

Phosphorus,  32,  37,,  37,  47,  51,  54,  55,  58, 

63,  67,  68,  82,  88,  95,  loi,  104 

Photosynthesis,  51 

Phyllopxxis,  121,  125 

Phylogeny,  108,  149 

Physicochemical,  changes,  74;  energy,  20, 
22, 48,  58,  95,  99,  150;  environment,  147, 
16O;  232,  254;  forces,  52;  laws,  14;  na- 
ture of  life,  2,  5,  6,  15;  processes,  14,  18 

Phytosaurs,  191,  193,  199,  211,  227 

Pigeon,  228  (Fig.) 

Pine,  108 

Pituitary  body,  75,  249-251,  289,  290 

Placentalia,  237;   see  Placentals 

Placentals,  236,  292;  see  Placentalia 

Placochelys,  203  (Fig.) 

Placodontia,  203 

Planetesimal  theory,  25,  26,  34 

Plankton,  91 

Plants,  23,  32,  ss,  41,  5i-53»  55,  56,  63,  66, 
67,  69,  70,  80,  87,  91,  99,  100,  105-109, 
no,  ni,  166,  217,  257,  285 

Plaiccarpiis,  210 

Platcosaurus,  216  (Fig.),  217 

Pleistocene,  135,  219,  236,  238,  255,  261 

Plesiosaur,  193-196,  200,  201,  206-208,  292 

Pliocene,  135,  236,  256,  261,  263,  266,  274 

Podokcsaurus,  211  (Fig.) 

Poisons,  73,  116;  see  Toxic  action 

Polychseta,  128 

Polyno'e  squamata,  128  (Fig.),  129 

Pools,  38,  84,  102,  180,  184,  189,  197,  198 

Porcupine,  224 

Porifera,  118,  131,  290 

Porpoise,  155  (Fig.),  200 

Parthcus,  209  (Fig.),  210 

Potassium,  ss,  36,  37,  47,  52,  54,  55,  63, 
64,  67,  68,  71,  82,  84,  loi 

Poulton,  Edward  B.,  7,  28,  144 

Predentata,  195,  221,  225 

Primates,  236,  237,  261,  274,  292 

Proboscidea,  261,  265,  269-273,  292;  see 
Proboscidians 

Proboscidians,  262,  263,  266,  269-271;  see 
Proboscidea 


Proboscis,  270,  271 

Procolophon,  191 

Proganosaur,  193 

Proganosauria,  201,  207 

Proportion,  75,  142,  208,  238,  248-252,  265, 

266,  268-270,  279,  282 
Protein,  49,  55,  58,  62,  66,  68,  70,  73,  74, 

87,  88,  89,  107,  247-249,  280,  288,  289 
Protilanotherium  cmarginatum,  264  (Fig.) 
ProtocctuSj  241 
Protochordates,  162,  246 
Protoplasm,  21,  22,  40,  46,  58,  61,  65,  77, 

85,  87,  91-95,  99,  106,  no,  114,  n6,  232, 

288;  origin  of,  37,  38 
Protozoa,  38,  50,  89,  90,  94,  104,  110-118, 

n9,  131,  143,  157,  206,  253,  254,  290; 

see  Organisms,  single-celled,  unicellular 
Psychic  powers,  114 
Ptcranodon,  226 
Plerichlhys,  166,  170  (Fig.) 
Pterodactyl,  226  (Fig.) 
Pterosaur,  193,  194,  211,  226,  227,  239,  292 
Ptyonius,  179  (Fig.) 
Pupin,  Michael  I.,  12,  13 
Pygmies,  273  (Fig.) 
Pyrenees,  83,  255,  256 


Quaternary,  161,  168,  178,  193,  227,  236, 
256 


Radioactive  elements,  28,  56 

Radioactivity,  see  Energy  of  radioactivity 

Radiolaria,  32,  115  (Fig.),  290 

Radium,  6,  n,  28,  41,  54,  56,  95 

Rangijcr  tarandus,  271  (Fig.) 

Rats,  271 

Rays,  168,  169,  292 

Reaction,  see  Action  and  reaction 

Reade,  T.  Mellard,  36 

Red  Sea,  102 

Redwood,  94,  96,  97 

Regeneration,  116,  198,  199 

Reichert,  Edward  Tyson,  79,  169,  245,  247 

Reindeer,  271  (Fig.) 

Reproduction,  17, 18,  20, 102, 103, 105, 116, 
152,  272 

Reptiles,  131,  137,  142,  161,  163,  165,  168, 
172, 178, 181, 275, 184-226, 231-233, 239, 
246,  253,  260,  266;  see  Reptilia;  flying, 
226,  292;    mammal-like,  190,  191,   236, 
292;  Permian,  201;  pro-,  185 


320 


INDEX 


Reptilia,  178,  180,  184-226,  231-233,  236, 
292;  see  Reptiles;  pro-,  189,  196 

Respiration,  16,  40,  53,  61,  72,  280,  289 

Retardation,  16, 17, 108, 145,  i49»  233»  252, 
268,  270,  279,  280 

Rheas,  230 

Rhinoceros,  260,  263,  264,  292;  woolly,  272 
(Fig.) 

Rhinoceros  t ichor hinuSt  272  (Fig.) 

Rhizopods,  114 

Rhizostomae,  129 

Rhodophyceae,  104 

Rhyncocephalia,  193,  201 

Rhytidodon,  199  (Fig.),  211  (Fig.) 

Richards,  Herbert  M.,  53 

Rocks,  83,  84;  see  Chalk,  Coal,  Gneiss, 
Granite,  Graphite,  Limestone,  Sandstone, 
Schists,  Shale;  decomposition  of,  83; 
igneous,  27,  31,  32,  36,  44,  153;  sedimen- 
tary, 29,  36,  100,  118,  153;  see  Sedimen- 
tary deposits;  stratified,  90;  volcanic,  32 

Rocky  Mountains,  136,  198,  205,  213,  217, 
218,  220,  255,  256,  261,  262 

Rodents,  236,  237,  239,  258,  259,  271,  272, 

292 
Rumford,  Benjamin  Thompson,  Count,  13 
Russell,  Henry  Norris,  44,  46 
Russia,  191 
Rutherford,  Sir  Ernest,  3,  11,  28,  56,  59,  97 


Sagitla,  120,  129;  gardineri,  129  (Fig.) 
St.  Hilaire,  Geoffroy,  158,  215,  279 
Salamander,  178 
Salt,    see    Ocean,    salt    in    the;     Sodium 

chloride 
Saltation,  63,  140,  252,  268,  277 
Sandstone,  65,  189,  198 
Saratoga  Springs,  102 
Saurischia,  210 

Sauropoda, 195, 196, 211, 213, 216-221,  266 
de  Saussure,  N.  T.,  51 
Saxony,  177 
Scales,  147,  179,  227 
Schafer,  Sir  Edward,  74 
Schickchockian  Mountains,  134 
Schists,  83 
Schizophyceae,  286 
Schleiden,  M.  J.,  93 
Schopenhauer,  A.,  8 
Schuchert,  Charles,  134,  136,  165,  171,  180, 

255 
Schwann,  T.,  93 


Scorpion,  125, 132, 133, 136,  291;  sea-,  132, 

133  (Fig.),  137 
Scotland,  170,  175,  177 
Scrope,  G.  Poulett,  24 
Scymnognathtis,  192  (Fig.) 
Scyphomedusae,  129 
Sea-cucumbers,   125-127   (Fig.),  291;    see 

Holothurian,  Holothuroidea 
Seals,  236,  237,  239 

Seas,  35,  90,  102,  104,  118,  119,  122,  181 
Sea-urchin,  94,  97,  291 
Sea-water,  37,  38,  9°,  io4 
Sedimentary  deposits,  90;  see  Rocks,  sedi- 
mentary 
Sedimentation,  28-30,  118 
Sediments,  26-28,  31,  197 
Seeley,  H.  G.,  189 

Selection,  20-22,  69,  99,  117,  i37,  140,  143" 
145, 147, 188,  225,  232,  233,  240,  241,  244, 
250,  268,  271,  279 
Semon,  R.,  144 
Semostomae,  130 
Scqtioia,  96  (Fig.),  97,  142;    sempervirens, 

96,  97;  washinglonia  (gigantea),  96,  98 
Seymour ia,  187  (Fig.) 
Shale,  32,  65,  100,  120,  122,  177,  189,  198 
Shark,  134,  i55  (Fig-),  161, 167-170  (Figs.), 
172,  204,  230,  292;  acanthodian,  161, 167 

(Fig.) 

Shell,  148,  202 

Shell-fish,  136 

Shore,  122,  197 

Shrew,  234,  239;   tree,  235  (Fig.),  236,  252 

Shrimp,  124  (F^ig.),  291 

Sierra  Nevada,  136,  218,  256 

Sierran,  135,  136 

Silica,  31,  32,  50,  68,  104 

Siliceous,  ooze,  104;   skeleton,  115 

Silicon,  33,  47,  54,  67 

Silurian,  50,  122,  ij?,  133,  135,  i53,  i54, 
161,  164-166,  168,  177,  178,  i93i  256 

Sirenians,  269,  270 

Skates,  169 

Skeletal,  structure,  185,  246;  system,  280 

Skeleton,  55,  63-65,  75,  115,  i53,  i54,  203- 
205,  220,  228,  230,  252,  259,  267;  cartilag- 
inous, 167 

Skin,  168,  187,  197,  289 

Skull,  185-187,  190,  270,  279 

Sloth,  239;  tree,  279 

Smith,  G.  Elliot,  235 

Smith,  Perrin,  137,  160 

Snakes,  186,  193,  194,  200,  231,  292;  see 
Ophidia;  sea-,  201 


INDEX 


321 


Sodium,  33,  35-37,  46,  47,  54,  55,  66,  71, 

82,  84;  chloride,  29;  see  Salt 
Soils,  83-85 
Solar,  heat,  43-45,  48,  51,  53^  see  Sun,  heat 

of;  spectrum,  44  (Fig.),  46  (Fig.),  47,  52, 

64,  65  (Fig.),  loi,  III,  113  (Fig.) 
SoUas,  W.  J.,  29,  36 
South  Africa,  171,  180,  184,  185,  189,  191, 

197,  207 
South  America,  125, 148, 180, 195, 196,  217, 

227,  237,  255,  256,  261 
South  Dakota,  16 r,  218 
S  pad  ell  a  cephahptera,  129 
Specialization,  137,  158,  159,  165,  167,  175, 

192,  260 
Spectrum,  solar;  see  Solar,  spectrum 
Speed,  153,  164,  221,  265,  266 
Spencer,  Herbert,  143,  232 
Sphargidae,  202 
Sphargis,  202  (Fig.) 
Spiders,  133,  291;  sea,  166 
Spines,  129,  161,  182,  188,  222,  224 
Spirifcr  mucronatiis^  138,  140  (Fig.) 
Spitzbergen,  205 
Sponges,  32,  130,  29Q 
S|X)res,  4Q,  103,  105,  iii 
Springs,  hot,  102,  103 
Spruce,  108 
Squamata,  186 
Squirrels,  239 
Starch,  52,  58,  107,  287 
Starfishes,  136  (Fig.),  172,  291 
Stars,  3,  7,  18,  47,  48,  59,  60,  62;  evolution 

of,  3,  7 
Slauraspis  stauracanlha ,  115  (Fig.) 
Stegocephalia,  178,  180,  186,  190,  292 
StegomuSj  211  (Fig.) 
Stegosaurs,  223,  224 
Stegosaurus,  224 

Sternoptyx  diaphana,  173  (Fig.),  174  (Fig.) 
Stimulation,  65,  66,  74 
Strasburger,  E.,  94 
Strontium,  33,  34,  54 
Struthiomimus ,  213-215  (Figs.),  229 
Sturgeon,  168,  170,  292 
Stutzer,  A.,  83 

Stylonnrus  excelsior,  133  (Fig.) 
Stxlophtlmlmiis  paradoxus,  173  (Fig.),  174 

(Fig.) 
Sudburian.  50,  153 

Suess,  Eduard,  34,  125,  171,  180,  255 
Sugar,  52,  86,  107,  286,  287 
Sulphur,  Z2>,  37,  47,  50,  54,  58,  62,  63,  67, 

68,  82,  83,  2>2>,  loi 


Sun,  4,  18,  22,  43-48,  51-53,  60,  1 13;  heat 
of,  43-45,  48,  49,  52,  56,  84,  no,  see 
Solar  heat;  -spots,  47,  61 

Sunlight,  43-45,  49,  51-53,  56,  84,  99,  105 

Suprarenals,  75,  289 

Survival  of  the  fittest,  20,  22 

Switzerland,  263 

Symbiosis,  87,  92 

Symbiotic,  adaptation,  158;  relations,  89 

Synapta  girardii,  126,  127  (Fig.) 

Synthetic,  enzymes,  89;  functions,  61 


Tables,  Lists,  and  Charts:  action,  reaction, 
and  interaction,  16,  280;  adaptation,  143, 
151,  156,  158,  201,  202,  227,  239,  243; 
animals,  118,  131,  237,  290;  chemical 
elements,  S5,  37,  4i,  51,  54,  (to  face)  67, 
88;  chronology,  29,  36,  50,  153,  161,  168, 
178, 193, 195,  211,  227,  236,  256;  climatic 
changes,  135;  four  complexes  of  energy, 
22,  99,  154;  habitat  zones,  131,  201,  202, 
239,  243;  phylogenetic  charts,  50,  161, 
168,  178,  193,  211,  227,  236 

Taconic,  135,  256 

Tadpole,  177 

Tail,  129,  178,  182-184,  186,  187,  207,  212, 
215,  224,  228,  259,  270 

Tapirs,  260,  263,  292 

Tasmania,  180 

Teeth,  64,  148  (Fig.),  149  (Fig.),  151,  166, 
181, 182,  184, 190,  192,  205,  209.  221,  225, 
229,  2sS,  240,  252,  257,  266,  271,  272,  276, 
290 

Teleosts,  168, 170, 173, 175,  292;  see  Fishes, 
bony 

Temperature,  25,  26,  43,  44,  48,  107,  135, 
160,  175,  192,  213,  227,  232,  254;  life 
dependent  on,  48-50 

Terebratida,  122,  123  (Fig.) 

Tertiary,  153,  161,  168,  178,  193,  194,  198, 
227,  231,  232,  236,  254-259,  263,  274 

Testudinata,  193,  231 

Tethys,  171,  188,  217 

Tetons,  104 

Texas,  180,  183,  185,  187-189,  191,  198 

Theriodont,  191 

Thermodynamics,  5,  12-14,  18,  22,  53,  117 

Therocephalians,  190 

Theropleura,  186 

Thcropoda,  195 

Thinopus,  175;  antiqiius,  176  (Fig.),  177 

Thymus,  75,  289 


322 


INDEX 


Thyroid,  66,  75,  250,  289,  290 

Tidal  stability,  27 

Tides,  35 

Tigers,  225 

Titanium,  33,  34,  47 

Titanothere,     149,     258    (Fig.),    263-265 

(Figs.),  270,  292 
Toad,  178,  292 

Tortoises,  193,  239,  292;  sea,  201 
Toxic  action,  67 
Trachodon,  197  (Fig.),  222,  223  (Fig.),  276; 

annectens,  222  (Fig.) 
Traquair,  R.  H.,  170 
Trematops,  182 
Trias,  216,  217 

Triassic,  135,  153,  161,  168,  178,  183,  189- 
191, 193-200,  203,  205-207, 210-212, 216, 
224,  226,  227,  236,  255,  256 
Triceratops,  225 
Tridactylism,  159 
Trillium^  96  (Fig.),  97;  sessile,  96 
Trilobites,  120,  121  (Fig.),  124,  125,  130, 

132,  171,  291 
Trimerorachls,  182 
Trinacromerion  oshorni,  208  (Fig.) 
Trinity-Morrison  time,  218 
Trituberculata,  236 
Tuateras,  193,  194,  231,  292 
Tupaia,  235  (Fig.) 
Turaco,  67 

Turtles,  190,  193,  194,  200,  202,  205,  231, 
239;  sea,  202  (Fig.),  203  (Fig.),  206,  239, 
292 
Tusks,  259,  260,  270 
Tylosaunts,  200  (Fig.),  209  (Fig.),  210 
Tyrannosaurus,  215,  224  (Fig.);    rex,  214 
(Fig.),  225;  see  Frontispiece 


Uintathere,  258  (Fig.) 
United  States,  180,  270 
Uranium,  28 


Varanops,  186  (Fig.) 

Varanus,  186 

Variation,  8,  117,  140,  145,  ^47,  ^45 

Velocity,  14, 97;  of  character,  see  Character 

velocity;  of  light,  11 
Vertebrae,  188,  189,  252,  270,  276 


Vertebrata,  131,  141,  146,  I54,  253,  292; 

see  Vertebrates 
Vertebrates,  50,  75,  109,  117,  130,  138,  if)o, 

168,  170,  175,  198,  218;  see  Vertebrata 
Viviparity,  204,  205 
Volcanic,    action,    29-31,    206;     ash,    19S; 

emanations,  68;   heat,  45;   islands,  213 
Volcanoes,  40,  62,  134,  171 
de  Vries,  Hugo,  7,  106,  107,  140,  144,  145 

W 

Waagen,  Wilhelm,  138-140,  276 

Walcott,  Charles  D.,  28,  29,  85,  118,  120, 

122,  126,  129,  160 
Wallace,  .\lfred  Russel,  24,  257 
Walrus,  239 

Wasteneys,  Hardolph,  iii 
Water,  9,  18,  22,  28,  $3,  34-39.  <o.  4i,  45, 

52,  55,  64,  68,  70,  83,  84,  91    105,  lo^t 

156,  285 
Watson,  D.  M.  S.,  189 
Weismann,  A.,  19,  20,  94,  95,  144,  i45 
Whales,  142,  200,  205,  234  (Fig.),  236,  237, 

239,  241,  247,  252,  259    260  (Fig.),  269, 

292 
Wheeler,  W.  C,  103 
Williston,  S.  W.,  180,  186,  209 
Wilson,  Edmund  B.,  92,  97 
Wing,  199'  226-230  (Figs.) 
Winogradsky,  S.,  82 
Wolf,  247 
Wolves,  225 

Woodward,  A.  Smith,  164 
Worms,  128,  136,  291;  see  Annulata 
Wortheru'lla  cambria,  128  (Fig.) 
Wurtemberg,  183 
Wyoming,  161,  197,  205,  217,  220,  221 


Xenon,  41 


X 

Y 


•jrapoK,  239 
Yeast,  42,  72,  287 
Yellowstone  Park,  103 


Zeuglodon,  200,  241,  242;  cetoides,  260  (Fig.) 
Zeuglodons,  269 
Zinc,  54,  56 
Zymase,  42 


ft 


t 


COLUMBIA   UNIVERSITY   I"" 


"his  br-k 


-*»» . 


0032019149 


Butler 
D575 


0sl2 


B'«»5St«>-^ 


m 


\^ /.,(..<.-    -^^-'''^tl^^^-^^^^-       ': 


'^i'-.--HW.^«* 


■^ 


■\ac% 


\o 


\-^ 


>^  *#■■«-  .^  -v- 


x^^. 


>y:-;-y.-vy/-'.'y.w.'..:.: 


k-lAiV 


^"•>iv^:r»f<- 


t>- 

-  • .    .V; 

.-    -;/ 

